BROWN beef and onion; drain. Stir in ketchup and mustard.
PRESS or roll each biscuit to 6-inch round. Fill with rounded 1/4 cup beef mixture, 2 tablespoons cheese and 2 pickle slices. Fold dough over filling and press to seal. Make 3 small slits in top of each. Place on large ungreased cookie sheet. If desired, brush tops with egg and sprinkle with sesame seed.
BAKE at 375°F 17 to 21 minutes or until deep golden brown.