Preheat your oven to 350°F.
Caramelize the onions and set aside in a bowl.
Add the ground beef, salt, and black pepper to a large skillet and brown on medium heat. After it browns, drain the grease.
Slice the sweet Hawaiian rolls in half and take the tops off. (Be careful to not pull each roll apart).
Line the rolls with a layer of cheese.
Spread the cooked ground beef on top of the cheese.
Place the caramelized onions on the top.
Next, top with more sliced cheese.
Place the top of the rolls over the cheese.
Place the sliders into the oven and bake for about 10 minutes or until the tops are golden brown.
After they bake, melt the butter, add the parmesan cheese and parsley, and brush over the tops.