Preheat oven to 350 degrees.
Cook broccoli according to package directions and drain. Arrange the spears in a greased 13x9 baking dish. Melt butter and saute onion for 3 minutes. Add chicken and cook until almost done and then place on top of the broccoli. Sprinkle the chicken breasts with garlic powder.
In a separate bowl, mix soup, mushrooms, mayonnaise, lemon juice, curry powder, and cayenne powder. Pour mixture over chicken and then sprinkle with shredded cheese.
TOPPING: Combine bread crumbs with melted butter and spread evenly on top of cheese. If using Panko crumbs do not use the butter.
Bake at 350 degrees for 30 minutes.