Cook bacon in a skillet over medium heat until crispy (8-10 minutes). Transfer to a paper towel-lined plate to drain and crumble.

In a mixing bowl, combine ground beef, crumbled bacon, panko bread crumbs, and milk. Gently mix until just combined.

In another bowl, whisk together egg, diced onion, minced garlic, Worcestershire sauce, Dijon mustard, smoked paprika, garlic powder, onion powder, salt, and pepper.

Pour the wet mixture into the meat mixture and combine gently.

Take a handful of meat mixture, flatten it, place cheese in the center, and fold over to form a meatball. Repeat until all mixture is used.

Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper and arrange meatballs. Bake for 20-25 minutes until golden brown.

Alternatively, pan-fry in a skillet with oil for 8-10 minutes until browned, then cover and cook for an additional 5-7 minutes.

Prepare burger sauce by mixing mayonnaise, ketchup, mustard, relish, and vinegar in a bowl. Refrigerate until serving.

Serve meatballs hot on toasted sesame seed buns with toppings like lettuce, tomato, red onion, and pickles.