- 5 minutes
- 20 minutes
- Preheat oven to 400 degrees.
- Dice onion.
- On rimmed 11x17 baking sheet, sprinkle onions and sprinkle with Worcestershire sauce.
- Using gloves or a piece of plastic wrap, spread ground chuck evenly over the top of onions all the way to edges.
- Sprinkle with salt and pepper.
- Place in preheated oven and cook for 18 to 20 minutes.
- While beef is cooking, slice rolls in half horizontally and squeeze mustard on bottom half of rolls (optional).
- Remove beef from oven and pour off the drippings.
- Top evenly with cheese and return to oven to melt.
- Using pizza cutter, slice beef into twenty four squares and place on rolls with a spatula (about 4 at a time)
- Replace top of rolls.