Fry ground beef, onion and peas in a skillet. Add garlic powder and pepper. Drain grease.
Add mushroom soup to mixture and transfer to a greased 9 x 13 inch casserole dish.
Boil 2-2/3 cup water, milk and butter in pan. When it comes to a boil, remove from heat and add the potato flakes stirring vigorously.
Spread the potatoes evenly over the hamburger mixture. Place cheese evenly on top of potatoes and sprinkle with paprika. Cover entire dish with tin foil and put in the oven at 375 degrees for 30 minutes. Remove tin foil and bake an additional 15 minutes or until cheese is slightly brown and bubbly.