Heat oven to 350°F. In medium bowl, mix beef, cheese, bread crumbs, parsley and onion. Press mixture evenly into 4 adjoining ungreased regular-size muffin cups at least 1 1/4 inches deep.
Bake 20 minutes. Meanwhile, in small bowl, mix salsa and buffalo sauce.
Remove muffin pan from oven; drain off fat. Spoon about 1 tablespoon salsa mixture over each loaf in pan.
Return to oven; bake 10 to 15 minutes longer or until meat thermometer inserted in center of loaf reads 160ºF. If desired, sprinkle loaves with additional parsley.