Creamy Mushroom-Chicken Casserole Recipe

Ingredients

• 1 tablespoon olive oil, or more as needed
• 2 skinless, boneless chicken breasts, diced
• 1 (8 ounce) package sliced fresh mushrooms
• 1 large onion, diced
• 3 tablespoons chopped fresh parsley
• 1 teaspoon paprika
• 1 teaspoon celery salt
• 1 teaspoon garlic powder
• 1 pinch salt and ground black pepper to taste
• 1/4 cup milk, or more as needed
• 6 ounces cream cheese, or more to taste
• 1 pound chopped, cooked broccoli
• 1/2 cup shredded Parmesan cheese
• 2 tablespoons butter
• 3 cups corn flakes, crushed, or more to taste