01 - Preheat oven to 400°F and line a baking sheet with parchment paper.
02 - In a skillet over medium heat, sauté the diced onion until translucent, about 3 minutes. Add ground beef, garlic powder, salt, and black pepper. Cook until the beef is browned, then drain and discard excess fat.
03 - Mix in ketchup, yellow mustard, Worcestershire sauce, and chopped pickles. Stir well to combine. Remove pan from heat and allow mixture to cool slightly.
04 - Flatten each biscuit round into a disc. On each, place 1 tablespoon of beef mixture and 1/2 tablespoon shredded cheddar cheese, then top with a mozzarella cheese cube.
05 - Bring dough edges up and around the filling, pinching firmly to seal and create a closed ball. Position seam side down on the prepared baking sheet.
06 - Brush each assembled bomb with beaten egg and sprinkle with sesame seeds.
07 - Bake in preheated oven for 15 to 18 minutes, or until golden brown and fully cooked.
08 - Let cool slightly on a wire rack before serving. Accompany with dipping sauces as desired.