Bake shoestring fries according to package instructions and set aside.
Spread butter on buns and set aside.
Heat a cast-iron pan or skillet on high for 3 to 5 minutes, or until very hot.
Place the beef balls in the pan, firmly smashing each one until it forms a thin patty. Season generously with salt and pepper. Cook until edges are browned, about 2 minutes.
Flip the patties but do not press. Season with salt and pepper. Cook for 1 minute, then add a slice of raclette to each patty. Cover and cook for 1 to 2 minutes, or until the cheese melts and the burgers are cooked medium. Set aside on a sheet pan.
Place the buns butter-side down on the hot pan and cook for about 1 minute, or until golden brown.