Savory Ground Beef Cheesesteak Sandwiches

Ingredients

• 1/2 teaspoon pepper
• 6 tablespoons softened butter
• 1/2 green bell pepper, diced
• 1 pound ground beef
• 1 small yellow onion, diced
• 12 slices provolone cheese
• 1 teaspoon salt
• 1 tablespoon olive oil
• 2 tablespoons Worcestershire sauce
• 1/2 cup diced portobello mushrooms
• 1 garlic clove, minced
• 6 crusty sub rolls