Preheat the oven to 375 degrees Fahrenheit.

Brown the ground beef in a large skillet over medium/high heat until it is no longer pink, breaking it up with a spatula as it cooks.

Add the ketchup, mustard, brown sugar, and salt to the skillet and stir to combine. Remove the skillet from the heat and set aside.

Place the rolls on a baking sheet or baking dish lined with parchment paper. Without separating the rolls, cut the tops off with a serrated knife and set them aside.

Arrange six slices of cheese on the bottom layer of rolls, and place it in the preheated oven for about 8 minutes until the cheese is melted.

Remove the bottom layer of rolls from the oven and spread the prepared meat mixture over the melted cheese.

Arrange the desired amount of pickle chips and crispy onions on top of the meat.

Lay the remaining six slices of cheese on top of the pickle/crispy onion layer.

Place the top layer of rolls back on the sliders and brush the melted butter evenly over the top.

Bake the sliders in the preheated oven for 12-14 minutes or until the tops of the rolls are golden brown.

Serve warm with fries.