Spray a 9x13-inch glass baking dish with cooking spray. In a skillet, melt the butter over medium heat. Add the bell pepper, onion, mushrooms; cook until tender, stirring occasionally. Drain if need be.
In a large bowl, beat eggs, sour cream, salt and pepper with wire whisk until well blended. Stir in the bell pepper mixture, green chilies and cheese. Pour into baking dish. Top with jalapeno slices.
Bake uncovered 45 minutes or until eggs are set.
Cut into squares and serve with optional topping on the side.