Set oven to 450℉. In a large skillet over med-hi heat, cook the ground beef stirring often until completely cooked. Drain excess grease. Slightly reduce heat and add onion for about 4 - 6 minutes. Stir in mustard, pickle, ketchup and pepper. Cook additional 2 - 3 minutes. Transfer to a pie dish and add the cheese on top.

Place pie crust over sealing at the edges. Cut four small vent holes in the center of the cheeseburger pie.

Bake for 15 minutes until crust is golden brown. Serve hot with mashed potatoes or fries.