Heat a saute pan on medium/high heat. Add the ground beef to the pan. Cook ground beef until browned, for 6-8 minutes.
1 pound ground beef
While the meat is cooking, dice the onion and green pepper. Make sure to remove the core and seeds from the green pepper.
1/2 medium white onion, 1/2 green pepper
Remove the pan then drain the beef.
Wipe the pan down and return it to the stove. Return the heat to medium/high and add the ground beef back to the pan. Then add the diced green peppers and onions, Worcestershire sauce, salt & pepper, ground mustard, and 1 clove minced garlic.
1 tablespoon Worcestershire sauce, 1/2 teaspoon salt, 1/2 teaspoon black pepper, 1/2 teaspoon ground mustard, 3 garlic cloves
Cook until the peppers and onions have softened, 4-5 minutes. Turn off the heat.
5 tablespoons butter
Preheat the oven to 375 degrees.
Spray a baking dish with olive oil spray. Add the mini-sub buns to the pan standing cut side up.
8 mini sub buns
Stuff the buns with the ground beef mixture evenly.
Sprinkle with cheese.
4 ounces shredded mozzarella cheese
In a microwave-proof mug or glass measuring cup, add the butter and put it into the microwave to melt for 30 seconds.
5 tablespoons butter
Add the remaining minced garlic. Stir.
3 garlic cloves
Slowly pour the melted butter on top of each ground beef cheesesteak that's in the baking dish.
Place the baking dish into the oven and bake the sandwiches for 8 minutes.