Preheat oven to 350 degrees F. Mix ground beef, onion, ketchup, mustard and Gravy Mix in large skillet until well blended. Cook and stir on medium-high heat until beef is no longer pink. Stir in cream cheese and 1/2 cup of the shredded cheese.
Spoon into 2-quart baking dish. Sprinkle with remaining 1/2 cup shredded cheese.
Bake 10 to 15 minutes or until cheese is melted. Sprinkle with tomatoes and pickles.