01 - Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.
02 - In a skillet over medium heat, sauté diced onion until translucent, about 3 minutes. Add ground beef, garlic powder, salt, and black pepper. Cook, breaking up meat, until browned. Drain excess fat.
03 - Stir in ketchup, yellow mustard, Worcestershire sauce, and chopped pickle. Mix thoroughly and remove from heat. Allow mixture to cool slightly.
04 - Flatten each biscuit into a round. Place 1 tablespoon beef mixture and 1/2 tablespoon shredded cheddar in the center of each. Top with one mozzarella cube.
05 - Gather edges of each biscuit round over filling, pinching tightly to seal and form a ball. Set seam side down on prepared baking sheet.
06 - Brush each filled dough ball with beaten egg, then sprinkle with sesame seeds for topping.
07 - Bake in heated oven for 15 to 18 minutes, or until the dough is golden brown and cooked through.
08 - Allow to cool slightly before serving. Offer additional burger sauces for dipping if desired.