Bratwurst Burgers with Braised Onions – Fustini's Oils & Vinegars

Ingredients

• 1 tablespoon Fustini's Garlic olive oil
• 1 large onion, sliced
• 1 medium sweet red pepper, sliced
• 1 medium sweet yellow pepper, sliced
• 1 cup dark beer or chicken broth
• 1/2 pound ground beef
• 1/2 pound uncooked bratwurst links, casings removed
• 1 tablespoon Fustini's 18 Year Traditional balsamic
• 1 large egg, lightly beaten
• 1 tablespoon 2% milk
• 3/4 cup seasoned bread crumbs
• 4 slices Muenster cheese
• 4 hamburger buns, split and toasted
• 8 teaspoons Harwood Gold horseradish mustard