Ingredients
1 tbsp. vegetable oil
1 tbsp. butter
1 large onion, chopped
Kosher salt
Freshly ground black pepper
1 tbsp. apple cider vinegar
1/4 c. mayonnaise
2 tsp. honey mustard
2 tsp. barbecue sauce
1 tsp. lemon juice
1 lb. ground beef
Kosher salt
Freshly ground black pepper
6 slices American cheese
4 tbsp. yellow mustard
3 potato buns, toasted
Iceberg lettuce
1 tomato, sliced
Preparation
Step 1Caramelize onions: In a large pan over medium heat, heat oil with butter. Add onion and cook until onion begins to sweat and turn golden, about 5 minutes. Reduce heat to medium-low and continue to cook until onions are soft, about 15 minutes more.Step 2Add a splash of water to pan, and scrape up any browned bits. Continue to cook until onions are jammy and caramel in color, adding a splash of water if onions start to dry out, about 10 minutes more.Step 3 Season with salt and pepper, then stir in vinegar.
Step 1In a small bowl, whisk together all ingredients.
Step 1Divide ground beef into six equal portions. Form meat into very thin patties (as thin as you can make them!). Season both sides with salt and pepper. Step 2Heat a large skillet (preferably cast iron) over medium-high heat. Working in batches, add patties to skillet. With a spatula, press down on patties to smash them even more. Spread a tablespoon of yellow mustard onto the raw side of each patty. When bottoms are seared and crusty, flip patties, about 4 minutes.Step 3Top each patty with a slice of cheese and cook until cheese is melty and burgers are cooked through, about 4 more minutes. Repeat with remaining burgers. Top each cooked burger patty with caramelized onions. Step 4Spread sauce onto each bottom buns then top with lettuce, a tomato slice, two burger patties, and the top burger bun.
As for the sauce, I tried (and tried…and tried) to match the taste of In-N-Out’s secret spread. But I failed miserably each time. So I gave up and turned to Chick-fil-A instead. You can’t beat mayo + barbecue sauce + honey mustard + lemon juice.
