Cook the mozzarella sticks according to package directions (I baked them but you could deep-fry them as well).
Add bacon to a large skillet and cook over medium heat, turning once, until it has turned brown in color and is crispy. Drain on a plate that is lined with paper towels. Drain any excess fat from the pan.
Form the ground beef into 4 equal patties and season on both sides with salt and pepper. Place the patties into the skillet that the bacon was cooked in. Cook over medium-high heat, turning frequently until fully cooked (the internal temperature has reached 160 degrees F.). During the last few minutes of cooking top each patty with a slice of American cheese. Cook until the cheese has melted.
Split the sesame seed buns in half and spread the butter onto the cut side of each bun. Place cut side down into a clean skillet and toast over medium heat until golden brown on the bottom (this can be done in a separate skillet while the burgers are cooking).
To assemble the sliders—place each burger onto the top of the bottom half of each bun. Top with 2 bacon slices and 1-2 mozzarella sticks per burger. Spread the BBQ sauce onto the bottom of the top half of each bun. Place it onto the burger, BBQ sauce side down.