Heat the oil in a skillet and add the meat.
Sauté until cooked through.
Set the meat aside and cook the onion and mushrooms in the same skillet.
Put the meat back in with the onion and mushrooms.
Add the broth, salt, pepper, and Worcestershire sauce.
Sauté until the liquid is thick and has cooked down.
Meanwhile, toast the slider buns under the broiler.
Spoon the meat mixture over the toasted bun bottoms.
Add mozzarella over before adding the tops.