Chicken and Zucchini Casserole with Creamy Polenta

This chicken and zucchini casserole is the kind of warm, cheesy, veggie-packed dinner that takes full advantage of the late-summer zucchini harvest while welcoming fall with open arms. Not that you can't make this any time of year, of course. But it is the kind of thing I most want to make in those in-between months when the days are warm but the nights are crisp and cool.

This casserole is a great way to use up leftover cooked chicken, or simply pick up a rotisserie chicken from your local grocery store. Because the chicken is already cooked, the casserole is also an easy way to turn leftovers into an entirely new dinner.

Smoked Gouda is my first choice because it adds an irresistible smoky richness, but mozzarella, Monterey Jack, provolone, or any melty cheese you like works perfectly well. 

Recipe creation, development, and writing by Rebecca Blackwell.

Recipe testing and photography by Anne Blackwell.

TL;DR

✔️ A complete meal in one dish

✔️ Packed with vegetables

✔️ Excellent use for leftover chicken

✔️ No canned soup

✔️ Big, interesting flavors

✔️ Naturally gluten-free

Ingredient notes

Polenta: The word "polenta" can be confusing because the same word is often used to describe dry, coarse-ground cornmeal and the cooked, finished dish that's made with the cornmeal. Packages labeled "polenta" indicate that the corn was ground to the best consistency for making polenta. You can use this interchangeably with regular or coarse-ground cornmeal or packages labeled "corn grits". Avoid finely ground cornmeal, which gives the finished dish a pasty, gummy consistency. As you can see in the photo above, I used Bob's Red Mill Organic Polenta.

Cooked Chicken: You'll need about 1 pound of cooked chicken for this casserole. This is an excellent use for almost any kind of leftover chicken, especially roast chicken. But a store-bought rotisserie chicken works just as well. Both white and dark meat work well, so use whichever you prefer, or a combination of the two. Chop or shred the chicken into bite-size pieces before adding it to the casserole.

Frozen Spinach: Frozen spinach is my go-to for this recipe because all the prep required is opening the bag and dumping it into the pan. No thawing required. But, you can certainly use fresh spinach if you like. If using fresh spinach, you'll want to increase the amount to 1.5 to 2 pounds. Wash and dry the spinach before using.

Basil Pesto: Prepared basil pesto provides much of the flavor in this casserole, so use one you know you like. I really like Delallo Simply Pesto. If you are cooking for someone with nut allergies, try making the pesto from scratch using sunflower seeds in place of the traditional pine nuts.

Cheese: Smoked Gouda is my first choice for this casserole. Its smoky, savory flavor is delicious with the pesto, chicken, and creamy polenta. But I often mix it with mozzarella, as I did in the casserole you see pictured here. Swap in any melty cheese you like. Monterey Jack, provolone, Gruyère, and Comté are all great choices. 

Step-by-step photos and instructions

Prepare a 9-by-13-inch rectangle baking dish by smearing the inside with about 1 tablespoon of softened or melted butter.

Add water, milk, and a bit of salt to a medium size saucepan and set it over medium-high heat.

When the liquid begins to boil, slowly pour in the polenta, stirring constantly with a wire whisk as you pour until it's all blended in.

Reduce the heat to low and cook, stirring frequently, for 15 minutes, until the polenta is very thick.

Pour it into the casserole dish and spread it out into an even layer. Set aside.

Chop the onion into pieces that are no larger than a pea and mince the garlic. Cut the zucchini in half lengthwise, then cut each half into slices that are about 1-inch thick. 

Add some olive oil to a large skillet along with the chopped onion. Cook, stirring occasionally, until the onions are soft and just beginning to brown.

Add the garlic, zucchini, Italian seasoning, and crushed red pepper. Cook, stirring frequently, for 2 minutes.

Add the spinach and cook for a few minutes until it's completely thawed.

Remove the pan from the heat and stir in the pesto and cream.

Add the chicken, stirring it around to coat in the sauce. Taste and add more salt if desired.

Spread half of the grated cheese over the polenta in an even layer.

Add the chicken and zucchini to the pan, spreading it over the cheese.

Top with the remaining cheese and place in the oven to bake.

Bake for about 25 minutes, until the casserole is bubbling around the edges of the pan and the cheese is completely melted. Let rest for 10 minutes before serving.

How to store this casserole and reheat leftovers

This casserole can be assembled in advance and stored in the refrigerator for up to 24 hours before baking. Please note that if you bake it straight from the refrigerator, it will require a longer baking time. Plan on an additional 15-20 minutes for the casserole to heat all the way through.

Leftovers reheat well in either the microwave or the oven. To reheat individual servings in the microwave, warm them in two-minute intervals until heated through. To reheat the casserole in the oven, cover it with aluminum foil to prevent the top from drying out, then place it in a 350°F oven until heated through.

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