Preheat the oven to 350 degrees F (175 degrees C). Spread chicken in the bottom of a 9x13-inch baking dish and scatter broccoli over top.
In a medium bowl, combine mayonnaise, curry powder, cayenne pepper, garlic salt, salt, and pepper, and mix well. Add 1 cup Cheddar cheese, cream of chicken soup, and cream of mushroom soup and mix again, then pour mixture over chicken and broccoli. Sprinkle with remaining 1 1/2 cups of cheese and top with onions.
Bake in the preheated oven for 30 minutes.
