Step 1

Preheat the oven to 350 degrees F (175 degrees C). Butter the bottom and sides of a 9x13-inch dish.

Step 2

Bring a pot of water to a boil. Add chicken and continue to boil until no longer pink, 5 to 10 minutes.

Step 3

Meanwhile, combine broccoli, cream of chicken soup, Cheddar cheese, 1/2 cup Parmesan cheese, mozzarella cheese, sour cream, and pepper in a large bowl. Mix well.

Step 4

Drain chicken and add to broccoli mixture. Mix well. Pour into the prepared baking dish and spread evenly.

Step 5

Bake in the preheated oven for 20 minutes. Add remaining Parmesan cheese on top and continue to bake until cheese is melted, 3 to 5 minutes.