01 - Preheat oven to 400°F and line a baking sheet with parchment paper.
02 - In a skillet over medium heat, cook diced onion until translucent, approximately 3 minutes. Add ground beef, garlic powder, salt, and black pepper. Sauté until beef is fully browned, then drain excess fat.
03 - Mix in ketchup, yellow mustard, Worcestershire sauce, and chopped pickles. Stir well, remove skillet from heat, and let filling mixture cool slightly.
04 - Flatten each biscuit round. Place 1 tablespoon of beef mixture in the center, add 1/2 tablespoon shredded cheddar, and top with a mozzarella cheese cube.
05 - Enclose the filling by bringing dough edges together and pinching to seal completely, forming a ball. Arrange seam side down on prepared baking sheet.
06 - Brush each dough ball with beaten egg and sprinkle with sesame seeds.
07 - Bake in preheated oven for 15 to 18 minutes until golden brown and baked through.
08 - Cool slightly before serving. Present with your choice of dipping sauces.