Double Cheese & Caramelized Onion Bacon Burger Recipe

Ingredients

• 1 tbsp. olive oil, plus more for drizzling
• 3 tbsp. butter, at room temperature
• 2 large or 3 medium onions, quartered and thinly sliced
• Salt and finely ground black pepper
• 1/2 cup beef consommé or beef stock
• 1 cup sour cream
• 8 slices meaty bacon
• 1 1/2–2 lbs. 80% lean ground beef
• Kosher salt and coarsely ground black pepper
• 2 tbsp. Worcestershire sauce
• 4 slices Swiss cheese
• 4 slices white American cheese
• 4 Euro-Bake Brioche Rolls, split
• 2 tbsp. Dijon mustard
• Pickle relish or sliced sandwich-size pickles
• Leaf lettuce or little gem leaves