Gourmet Patty Melts

Ingredients (12)

• + 1 pound ground sirloin add to pantry
• + 1 tablespoon Worcestershire sauce add to pantry
• + 2 cloves garlic, minced, or more to taste add to pantry
• + ½ teaspoon salt add to pantry
• + ½ teaspoon ground black pepper add to pantry
• + 3 tablespoons unsalted butter add to pantry
• + 3 tablespoons olive oil add to pantry
• + 2 medium onions, sliced add to pantry
• + cooking spray add to pantry
• + 4 slices Cheddar cheese add to pantry
• + 4 teaspoons Dijon mustard add to pantry
• ✓ 8 slices rye bread, lightly toasted