I cannot think of a more autumn vegetable than squash—any kind from pumpkins, to butternuts, to Acorn. Squash is comfort food that can be served at breakfast—maybe in a hash or just roasted with maple syrup—enjoyed at lunch—as in little squash bowls filled with hearty grains—or for dinner, which is where we are landing today. A Squash and Potato Casserole that can be a weekend meal with plenty of leftovers or the star attraction for that Thanksgiving buffet.
Now it is true that this casserole takes some time and some prepared ingredients, but there are make-ahead options for most of the prepared components and a lot of flexibility, allowing you to use what you like and what you have on hand. The only must-have here, in my opinion, is that combination of butternut squash, sweet potatoes and white potatoes—and even some flexibility is possible with those.
Let’s dive into the recipe first, and I will offer some make-ahead options as we go. Then, after the recipe we’ll look at each “layer” individually and think about substitutions and other options to suit preferences and availability of ingredients. One note: I was a very lucky green gal this fall and got some beautiful fresh Aleppo peppers from my farm friend Frank Biver. While Aleppo pepper is commonly used as a dried spice, I decided to use them fresh (while saving all the seeds for Frank so we will have more next year, right?). Just as dried Aleppo peppers add a flavor incomparable to other pepper flakes, the fresh diced peppers proved to be just as special. But I doubt you’ll find fresh ones any longer now, even if you could have found them at all before it turned cold. So, we’ll go over some substitution possibilities for this very special ingredient, too.
Let’s butter those casserole dishes and begin!
- Two cups finely processed stale cornbread (Use your favorite recipe and let it dry out in your fridge. Can be made up to a week in advance. See notes under the recipe for other options.)
- One tablespoon each whole coriander, whole cumin seed, whole mustard seed, crushed
- Two tablespoons fresh herbs to taste (Any herbs will work; I chose fresh fennel fronds, thyme and sage.)
- Salt and Pepper to taste (depends on your cornbread recipe)
- Three to four tablespoons unsalted butter
- A bouquet of herbs—whatever you like tied with kitchen string. (I chose a sprig of sage, a sprig of thyme and a sprig of rosemary.)
- One small, minced shallot or one quarter cup minced yellow onion (I used shallots.)
- Three to four tablespoons all-purpose flour
- Two and a half cups vegetable stock, simmering
- Pinch of sea salt (If you don’t make your own stock, check the taste for saltiness before adding salt to your roux. Velouté should not overpower on its own. It’s the vehicle for making everything else rich and creamy.)
- Two to three tablespoons olive oil
- Two tablespoons unsalted butter
- Two cups thinly sliced yellow onion, shallots or a combination of both (I did the combo.)
- Four large cloves garlic, crushed and chopped
- One-half cup chopped fennel
- One-half cup diced fresh Aleppo pepper, or pepper of choice (see options below)
- Coarse sea salt
- One-half cup dry white wine or sherry
- One small butternut squash, washed, peeled, seeded and sliced thin (I used my mandoline for slicing squash and potatoes.)
- Two large sweet potatoes, washed, peeled and sliced thin
- Two large white potatoes (such as Idaho Russet), washed, peeled and sliced thin (note the white potatoes can be prepped several hours in advance and kept refrigerated in an ice water bath. In fact, this is preferred, as it will take away the starchiness and your potatoes will bake better.)
- About two cups white cheddar cheese
- Simply use a large-capacity food processor to create a coarse, consistent crumb from your stale cornbread, adding all the seasonings along with the torn apart stale cornbread. This step can actually be made well in advance—several weeks, in fact. Once you have the cornbread crumble complete, store it in well-sealed containers in your freezer until needed. Then give it a quick thaw on your counter as you are preparing the rest of this dish. Having this tasty crumb topping mixture on hand in single-use containers is a handy way to make dinner preparations easy-peasy.
- This classic white sauce is best prepared using a bain-marie—which is nothing more than a big heat-proof bowl (think Pyrex) placed atop a large Dutch oven that has been filled with water until it barely touches the bottom of the bowl. The use of the bain-marie all but eliminates the unfortunate possibility of having your butter burn or your roux separate and fall apart. The diffused heat of the bain-marie gives you complete control.
- So set up the bain-marie and heat the water. Caution is needed to watch that the water does not boil too aggressively and that you keep your hand/arms clear of escaping steam around the sides of the bowl. Put on your stock and bring it to a gentle simmer—not a boil.
- Add the butter to the now-warmed bowl of the bain-marie and gently whisk it around until it melts. Add a sprinkle of salt, your diced onion or shallot and your herb bouquet. Once the butter has melted and is starting to sizzle, add the flour to form your roux. Continue whisking and cooking until the roux is thickened, smoothed out and the flour has sufficiently lost its raw edge—this all takes about six minutes.
- Now that you have a smooth roux, gradually add the hot stock, ladle by ladle, whisking in between each addition, until you get the consistency you want—a semi-thick white sauce that lives up to its name—velvet. You will likely have extra stock, so that’s good in case you need to adjust the velouté later—highly likely if you have made ahead and stored in the refrigerator.
- Remove from heat carefully using oven mitts to hold the bowl. Allow this mixture to cool about five minutes. Take this opportunity to remove the herbs. When you can safely handle the bowl, strain the cooled velouté through a fine mesh strainer into a bowl, cover the bowl with plastic wrap and refrigerate until needed. Be sure to cover it well or it will form a skim on the surface. Can be made a day in advance, then brought to room temperature before using. Adjustment may be needed regarding thickness.
- Add the olive oil and butter to a large chef's skillet to give your onions and shallots lots of area to brown and caramelize. Heat to medium-high and add the onions and shallots. Add a generous sprinkle of coarse sea salt. Cook and stir until the onions start to sweat. Reduce heat to medium-low and continue to watch, stirring occasionally as you prep the next set of vegetables: garlic, fennel and peppers.
- It will take the onions and shallots about 40 minutes to caramelize adequately. At this point, add the garlic and cook another five minutes. Next add the fennel and the pepper with another pinch of salt and cook another 10 minutes.
- Once everything has cooked down and there is some nice fond starting to stick to the skillet, turn up the heat and add the wine to deglaze. Allow this to cook down until the skillet is almost dry and all the rich flavor has concentrated. Remove from heat and either keep warm or store in the refrigerator until needed.
- To Prepare Squash and Potatoes Slices
- Begin with the white potatoes, washing, peeling and slicing thin, preferably with a mandoline. Place the slices in a bowl of ice water and refrigerate until needed, at least four hours and up to eight.
- Now prepare and slice the sweet potatoes and butternut squash. Since measurement is not precise with these vegetables, you may have leftover slices that won’t fit into the layered casserole, but these will be handy in soups and sautés later, so yeah! Better too much than not enough here. Pack your layers with these super-thin slices, as they will soften and absorb all the flavors they are sharing space with in the casserole—don't be skimpy.
- Preheat the oven to 375 degrees. Generously butter a 13 x 9 casserole dish.
- If the velouté has been in the refrigerator, bring out ahead so it will warm up a bit. You’ll want to stir this well to see if it has thickened up more than you want. Thin it with a bit of extra stock, if necessary.
- Grate the white cheddar cheese. A large grate is preferred here. Set aside until needed.
- Drain your white potatoes and pat completely dry.
- Assemble all your layer ingredients at the ready. Begin by placing a layer of squash and potatoes on the bottom of the casserole. On top of the squash layer add a layer of onions and peppers. Sprinkle with a layer of cheese. Keep repeating this until you reach the top of the casserole or run out of layer ingredients. Keep a bit of cheese to top the cornmeal crumble, if possible.
- Before topping with the cornmeal crumble, pour the velouté evenly over the entire casserole, trying to get it distributed throughout the layers.
- Finish the casserole with a very thick layer of cornmeal—use it all if you can—and sprinkle with any extra cheese.
- Cover the casserole with foil and bake for about 40 minutes, until the sauce is bubbling up through your layers and the potatoes and squash are fork tender. Uncover and bake another 10-15 minutes to brown the topping.
- Allow the casserole to rest for about 10 minutes before serving.
How I calculated the prep time: There are four major layers in the casserole, plus the cheese. I averaged out an hour per layer for prep--some will take a bit less, some a bit more. I strongly suggest not doing this all in one day, though I actually did that to develop the recipe. Of course, the cornbread was made way ahead as that was necessary to dry it out.
Tips on Tradeoffs
Velouté Variables: I’ve made my velouté with vegetable stock—my own stock from local vegetable scraps. But velouté can be made with any stock, and for this dish chicken will work well if you are not vegetarian and have some handy. I would avoid beef stock, as it will be stronger. Further, the herbs and shallot that I used don’t have to be what you use. Onions and leeks, diced small, work just as well. And any fresh herbs you like will work. Sometimes I’ve even grated in a bit of fresh nutmeg or citrus zest. So go for what you love!
Crumble Crafting: I just love it when I have something that seems to have surpassed its usefulness but can be turned into something wonderful, like stale cornbread transformed into a spicy, crunchy crumble. But if cornmeal is not your thing, you can use other ingredients to create a lovely topping, like plain old stale bread drizzled with herbed butter and a bit of the recipe cheese. Panko is another option, seasoned with spices and herbs. Each change, of course, changes the flavor profile. And I must admit, the cornbread worked really well—a beautiful flavor balance.
Cheese Choices: That cheddar I used? Doesn’t have to be that cheddar you use. I think Parmesan or Gouda would be lovely. You’ll want something with a sharper edge, so probably not a creamy goat cheese or a mild Swiss or Farmers cheese. But maybe Asiago? You’ll figure it out. There is no rule against mixing cheese either. I do it all the time—use up what you have! I did stay local by choosing my cheddar from Marcoot Jersey Creamery in Greenville, IL.
Other Aromatic Combos: As I mentioned above, I was lucky to have some fresh Aleppo peppers for this casserole. But it is likely you won’t. I suggest one of two options: red poblanos or red bell peppers in the designated amount. If you go with the bell pepper option, a bit of ground Aleppo pepper will really give it some zing—available at Penzeys Spices. Add the ground Aleppo pepper at the very end of your sauté step. And, if fennel is not your thing, celery is just fine.
Squash and Potato Possibilities: I think this is the one set of ingredients I would suggest not changing, if that’s possible. The combo of butternut squash, sweet potato and white potato gives the dish a lot of interest. I do think just butternuts and white potatoes, or sweet potatoes and white potatoes might work. Sweet potatoes and squash might be a bit much. I’m not sure you would get the nice blend of flavors you will get with more variety.
Ahh, casseroles. They are the ultimate in comfort food, yes? They make a ton, feed an army and warm up for leftovers with ease. Perfect as we enter the seasons of major cooking and large dinner parties on blustery winter days. Here are a couple more options from this blog: Pumpkin and Potato Gratin and my sophisticated take on the classic Green Bean Casserole, as side dishes take center stage. Then there is Irish Colcannon, a new riff on that old favorite–the Artichoke Heart Dip Casserole and a vegan Winter Wheatberry Bake.
Holidays are here! We’re off and cooking….