Philly Cheese Steak Sloppy Joes (Easy 25-Minute Dinner)

Ingredients

• 1 tablespoon olive oil
• 1 lb (450 g) 80/20 ground beef
• 1 small yellow onion, finely diced
• 1 green bell pepper, finely diced
• 1 cup (75 g) mushrooms, finely chopped
• 2 cloves garlic, minced
• 1/2 teaspoon kosher salt, plus more to taste
• 1/2 teaspoon black pepper
• 2 tablespoons ketchup
• 1 tablespoon Worcestershire sauce
• 1/2 cup (120 ml) low-sodium beef broth
• 1 tablespoon cornstarch
• 6 slices provolone cheese
• 4 hamburger buns or potato rolls
• 1 tablespoon softened butter, for toasting buns