Juicy Philly Steak Sloppy Joes with Sweet Caramelized Veggies - Yummy Gusto

Ingredients

• 1 pound thin ground beef
• 1 small yellow onion, chopped
• 1 small green bell pepper, chopped
• 8 ounces brown mushrooms, finely chopped
• 2 tablespoons tomato ketchup
• 1 tablespoon tangy Worcestershire sauce
• 1/2 teaspoon plain salt
• 1/2 teaspoon coarse black pepper
• 1 tablespoon corn thickener
• 1 cup beef stock
• 2 tablespoons unsalted butter
• 8 ounces Provolone cheese slices, cut into bits
• 6 soft brioche burger buns