Melt 1 teaspoon of butter in a large skillet over medium heat. Add finely chopped onions and cook 5 minutes until golden brown, stirring occasionally. Cool slightly.
Mix mayonnaise, both cheeses, parsley, garlic powder and hot pepper sauce in a medium bowl. Stir in onions and spoon into a baking dish.
Bake in a 350 degree oven for 20 or 25 minutes or until heated through. (I have used my toaster oven with a flat bowl that fits.) Serve on triscuits, club or ritz crackers. I like the new triscuit thin crisps best.