Heat oven to 350 degrees. Melt butter in very hot skillet and saute potatoes until brown. Reduce heat to medium and add ham;saute 1 minute. Heat oil in another medium-hot skillet and add mushrooms;saute until soft;season with paprika, thyme, cayenne, garlic powder, salt and pepper. Add mushrooms to ham mixture and toss lightly to combine. Coat a 3-qt casserole with vegetable spray and pour ham-mushroom mixture into casserole. Beat eggs in mixing bowl with milk until frothy. Season with salt and pepper. Pour eggs over ham-mushroom mixture. Bake at 350 degrees for 30 minutes, then arrange tomato slices around top and sprinkle with grated cheese. Return casserole to oven and bake until eggs are set, cheese is melted and top is brown. Sprinkle with parsley.