By An Edible Mosaic
For the topping, stir together all ingredients in a bowl.
For the homemade Cream of Chicken Soup, melt the butter in a saucepan and whisk in the flour. Whisk in the milk, chicken broth, dried onion, salt, garlic powder, and black pepper, and bring to a boil. Boil until thickened, then whisk in the cream cheese.
Add the chicken, mozzarella, cottage cheese, sour cream, scallion, and sauce to a large bowl and mix to combine.
Pour the filling into a 9 by 9-inch baking dish (or equivalent) sprayed with olive oil spray, and spread it out. Sprinkle the Ritz mixture evenly on top of the filling. Bake uncovered until the casserole is golden on top and bubbling.