Cook the Bacon: Heat a large skillet over medium heat, add diced bacon, and sauté for about 5–7 minutes until crispy. Transfer to a paper towel-lined plate to cool and crumble.

Mix Meatball Ingredients: In a mixing bowl, combine ground beef, crumbled bacon, panko bread crumbs, and ¼ cup milk. Mix until just combined.

Prepare Wet Ingredients: In a separate bowl, whisk together egg, chopped onion, minced garlic, Worcestershire sauce, Dijon mustard, smoked paprika, garlic powder, and onion powder.

Combine Mixtures: Pour the wet ingredients into the meat mixture and season with salt and black pepper. Mix gently.

Stuff with Cheese: Take meat mixture, flatten, add a cube of cheddar cheese, and shape into a meatball to seal the cheese.

Baking Method: Preheat oven to 400°F (200°C). Arrange meatballs on a lined baking sheet and bake for 20–25 minutes until golden brown.

Pan-Frying Method: Heat oil in a skillet, cook meatballs for 10–12 minutes, turning occasionally until browned.

Make Burger Sauce: Whisk mayonnaise, ketchup, yellow mustard, sweet pickle relish, and white vinegar until smooth. Chill in the refrigerator.

Assemble and Serve: Place cooked meatballs on toasted buns, top with lettuce, tomato, onion, and pickles, and serve with sauce.