1. On a work surface, place the beef slices 2 by 2, slightly overlapping them. Season with salt and pepper. Add a few pieces of onion on each slice and roll.
2. To keep the food in place during cooking, use 2 skewers at a time. On 2 skewers, pierce a roll of beef and onion, then a piece of cheese. Follow with a roll of beef, a cube of cheese, and finish with a roll of beef.
3. In a pan, melt the butter. Add the skewers and cook for 2 minutes on each side, or until the cheese cubes have taken on a nice golden color. Only turn the skewers once.
4. Remove the skewers from the pan and serve immediately.