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Cheesy Chicken Broccoli Casserole

Cheesy Chicken Broccoli Casserole is the kind of comforting dinner that brings together tender chicken, fresh broccoli, creamy sauce, and plenty of melted cheese in one bubbling dish. It is hearty enough for a family dinner, simple enough for a busy weeknight, and flexible enough to use leftover cooked chicken when you want to save time.

The secret to a flavorful casserole is building each layer with seasoning rather than relying only on the cheese. Lightly seasoned chicken, perfectly tender broccoli, a creamy sauce, and a golden cheese topping come together to create a dish that is rich without being complicated.

Ingredients

For the casserole:

3 cups cooked chicken, shredded or chopped into bite-sized pieces
4 cups fresh broccoli florets
2 tablespoons butter
1 small yellow onion, finely diced
2 cloves garlic, minced
1 can (10.5 ounces) cream of chicken soup
1 cup sour cream
½ cup chicken broth
1 teaspoon Dijon mustard
½ teaspoon garlic powder
½ teaspoon onion powder
½ teaspoon paprika
½ teaspoon salt, or to taste
¼ teaspoon black pepper
1½ cups shredded cheddar cheese
½ cup shredded mozzarella cheese
½ cup breadcrumbs
1 tablespoon melted butter
2 tablespoons grated Parmesan cheese

Step 1: Prepare the Oven and Baking Dish

Begin by preheating your oven to 375°F (190°C). Lightly grease a 9-by-13-inch baking dish with cooking spray or a small amount of butter.

Preparing the dish first makes assembly easier and prevents the creamy sauce and melted cheese from sticking around the edges.

Step 2: Prepare the Broccoli

Bring a pot of lightly salted water to a boil. Add the broccoli florets and cook for about 2 to 3 minutes, just until they become bright green and slightly tender.

Drain the broccoli immediately and, if desired, rinse it briefly with cold water to stop the cooking process.

The broccoli should not be completely soft at this stage. It will continue cooking in the oven, and starting with slightly crisp broccoli helps prevent the finished casserole from becoming watery or mushy.

Step 3: Sauté the Onion and Garlic

Melt the butter in a large skillet over medium heat. Add the diced onion and cook for approximately 3 to 4 minutes, stirring occasionally, until it becomes soft and translucent.

Add the minced garlic and cook for another 30 seconds. Be careful not to let the garlic brown too much, as it can become bitter.

This simple step gives the casserole a deeper savory flavor than simply mixing everything together cold.

Step 4: Make the Creamy Sauce

Reduce the heat to low and add the cream of chicken soup, sour cream, and chicken broth to the skillet.

Whisk or stir until the mixture becomes smooth and well combined.

Add the Dijon mustard, garlic powder, onion powder, paprika, salt, and black pepper. Stir everything together and allow the sauce to warm gently for about 2 to 3 minutes.

Taste the sauce before assembling the casserole. Adjust the salt and pepper if necessary.

The sauce should be creamy and spoonable. If it appears extremely thick, add another tablespoon or two of chicken broth.