In a small bowl, whisk together all the special sauce ingredients until smooth. Set aside.
In a large skillet over medium heat, cook the ground beef seasoned with salt, pepper, and garlic powder. Break it up into small crumbles and cook until browned. Drain excess grease.
Preheat your oven to 350°F (175°C).
Slice the slider buns in half horizontally (keep them connected if possible). Place the bottom halves in a greased 9x13-inch baking dish.
Spread a thin layer of special sauce over the bottom buns. Top with an even layer of cooked beef, then lay the cheese slices over the beef. Add pickle slices and shredded lettuce.
Place the top halves of the buns over the fillings. Brush the tops with melted butter. Cover loosely with foil and bake for 15 minutes. Remove the foil and bake for another 5 minutes until golden brown.
Slice into individual sliders and serve immediately with extra sauce on the side if desired.