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
½ 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 brioche or potato burger rolls, split
2 tbsp. Dijon mustard
Pickle relish or sliced sandwich-size pickles
Leaf lettuce or little gem leaves
Preparation
Step 1
Preheat the oven to 375°. In a large skillet, heat 1 tbsp. oil, one turn of the pan, over medium. Add 1 tbsp. butter; when it melts, add the onions, season with salt and finely ground pepper and cook, stirring occasionally, until deep golden brown, 30 to 35 minutes. Transfer to a medium bowl and mix in the consommé; let cool. Mix in the sour cream.
Step 2
Meanwhile, arrange the bacon in a single layer on a slotted broiler pan or on a wire rack set inside a rimmed baking sheet. Bake until very crispy, about 30 minutes. Cut the bacon in half crosswise. Preheat the broiler.
Step 3
In another medium bowl, season the beef with kosher salt and coarsely ground black pepper; mix in the Worcestershire sauce. Form into 4 patties (thinner in the centers for even cooking).
Step 4
Heat a cast-iron skillet or griddle over medium-high. Drizzle the skillet with oil, add the patties and cook 7 to 8 minutes, turning occasionally. Top each patty with 1 slice each of Swiss and American cheese during the last minute or two of cooking; tent loosely with foil to melt the cheese.
Step 5
Toast the buns under the broiler until golden brown, about 2 minutes.
Step 6
In a small bowl, mix the mustard and remaining 2 tbsp. butter; spread over the bun bottoms. Top each with relish or pickles, lettuce, a cheeseburger and 4 half-slices of crispy bacon so every bite gets an even amount of bacon. Slather the bun tops with onion sauce and set in place.
