Preheat Oven:
Preheat the oven to 350°F (175°C).

Cook Beef and Onion:
In a large skillet, cook the ground beef and onion over medium heat until the beef is no longer pink and the onion is tender, usually about 3-4 minutes. Break up the beef into crumbles while cooking. Drain any excess grease.

Prepare Filling:
Stir in the crumbled bacon, ketchup, mustard, and chopped pickles or relish into the beef mixture. Allow the mixture to cool slightly.

Roll Out Biscuits:
On a lightly floured surface, roll out each biscuit into a 5-inch circle.

Assemble Bombs:
Place 1 tablespoon of shredded cheddar cheese in the center of each biscuit round. Top the cheese with about 2 tablespoons of the prepared meat mixture. Bring the edges of the biscuit dough over the filling to the center and pinch to seal, forming a bomb shape. Ensure the seam side is facing down.

Brush and Sprinkle:
Brush the tops of the bombs with beaten egg and sprinkle sesame seeds over them.

Bake:
Place the assembled bombs on a parchment-lined baking sheet and bake in the preheated oven until they turn golden brown, which usually takes about 18-20 minutes.

Serve:
Serve the cheeseburger bombs warm and enjoy the deliciousness!