Add meat to cheese mixture; stir to mix. Place in a baking dish that holds 4 C (1 L). Bake until bubbly, about 20 min. Sprinkle with tomatoes, topper, and onion and parsley, if desired. Serve with veggies and pita chips, if desired.
Tip: Make it vegetarian: swap beef for veggie ground round or canned lentils.
Make Ahead: Prepare dip. Cover and refrigerate up to 3 days before serving, or freeze up to 1 month. Defrost before baking.