Ingredients
1 tbsp. extra-virgin olive oil
1 large red onion, cut into half moons
1 tbsp. brown sugar
1 tbsp. balsamic vinegar
1/4 c. red wine
kosher salt
Freshly ground black pepper
1 1/4 lb. ground beef
1 Garlic clove, minced
1 tbsp. finely chopped fresh rosemary
3 oz. Gruyere, thinly sliced
1/4 c. grainy Dijon mustard
4 potato hamburger buns (or other hamburger buns)
Lettuce, for serving
Tomato, for serving
Preparation
Step 1In a large sauté pan over medium-high heat, heat oil. Add onions and cook until beginning to soften, 4 minutes. Stir in brown sugar and balsamic vinegar and cook until beginning to caramelize, another 3 minutes. Add wine and let simmer until evaporated, 2 to 3 minutes, then season with salt and pepper.Step 2Preheat broiler to high.Step 3In a large bowl, combine ground beef, garlic, and rosemary and season generously with salt and pepper. Combine mixture thoroughly with your hands and shape into 4 patties. Season patties with salt and pepper on both sides.Step 4Heat a lightly oiled grill pan over high heat, cook for 3 minutes, then flip. Add Gruyere to the burgers and cook an additional 3 minutes. Transfer pan to broiler until cheese completely melts, 15 to 30 seconds.Step 5Spread bottom of each bun with 1 tablespoon Dijon mustard. Top with burgers, balsamic-glazed onions, and tops of buns, and serve with lettuce and tomato.
