Preheat oven to 350 degrees. Place the buns on a baking sheet lined with parchment paper.
Using a small knife make a hole in the top of each slider, making it big enough for the meatballs to fit in, but don’t cut all the way through. (Keep in mind that the meatballs are not meant to fit entirely inside the hole, only half way.)
In a small bowl, stir together melted butter, minced garlic and parsley. Brush the butter mixture into the hole of each bun.
Put a pinch of mozzarella cheese into each hole. Place a meatball into each hole. Spoon a little pasta sauce over each meatball. Cover the meatballs with remaining mozzarella cheese and sprinkle with parmesan.
Cover the dish with foil and bake for 10 minutes, then remove the foil and continue baking for an additional 10 minutes. Remove from the oven and top with fresh chopped basil.