In a large skillet over medium-high heat, cook the onions in olive oil and butter under soft and translucent.
2 tablespoons olive oil, 1 small onion, 8 tablespoons butter
Add the minced garlic and cook 1-2 minutes more until fragrant.
3 cloves fresh garlic
Stir in the cream soup, sour cream, and seasonings.
1 10.5 ounce can cream of chicken soup OR homemade cream soup substitute, ½ cup sour cream, 1 teaspoon poultry seasoning or favorite herb mix, kosher salt and black pepper
Slowly whisk in the milk a little at a time until the sauce reaches your desired consistency.
2 cups whole milk
Next, mix in all of the parmesan cheese and 2 cups of the mozzarella cheese. Remove the pan from the heat and stir until the cheeses melt.
⅓ cup parmesan cheese, 2½ cups mozzarella cheese
Toss the cooked chicken and pasta into the creamy cheese sauce.
3 cups shredded chicken, 1 lb rotini pasta
Transfer the chicken mixture to the prepared baking dish.
Top with remaining ½ cup of mozzarella cheese.
Mix together 6 tablespoons of melted butter with the breadcrumbs and mix with a fork. Sprinkle over the top of the casserole.
1 cup panko breadcrumbs
Bake for 30-35 minutes until golden brown and bubbly.