Whether you’re looking for exciting new ways to enjoy more greens and veggies, or you have a garden bursting with this yummy summer squash, you can’t go wrong with this cheesy cheddar and parmesan zucchini casserole recipe. Zucchini, like cauliflower, is mild and super versatile, making it the perfect vegetable for casseroles, picky kiddos, or anyone hoping to fill their dinner plates with more greens. Made with super simple ingredients like fresh zucchini, creamy mayonnaise, sour cream, and plenty of cheese, everyone will love this recipe – guaranteed! Serve it as a low-carb side dish with your favorite main dishes, or add it to your holiday meal plan.
Prepare the zucchini: Slice the zucchini into 1/4-inch rounds, toss in 1-2 teaspoons salt, and place in a colander set of the sink. After the zucchini has drained, transfer them to a clean kitchen towel lined with paper towels. Gently pat the zucchini dry.
Saute the onions: Cook the onions and garlic in butter or olive oil until softened. Prepare the creamy cheese mixture: Combine the sour cream, mayonnaise, eggs, grated parmesan cheese, ½ cup of shredded cheddar cheese, and ½ cup of mozzarella cheese in a large bowl. Add the softened onions once cool, mixing well.
Assemble: Arrange the zucchini slices in overlapping rows (see image). Pour the creamy onion and cheese mixture over the top and smooth the surface with a wooden spoon.
Bake for 20 minutes, then carefully remove from the oven. Meanwhile, as the casserole is baking, melt the remaining two tablespoons of butter in a small bowl and combine with the panko breadcrumbs. Top with panko and bake again.