Double Smash Burger with Caramelized Onions and House Sauce

Method

1. Slice the onions 3 mm thick from root to tip. Melt the butter in a 24 cm pan over medium heat, add the onions and salt and cook for 5 min, stirring, until soft and translucent. Turn down to medium-low heat and cook for 20 min, stirring every 2 to 3 minutes; whenever brown bits stick to the bottom, add 1 tbsp water and scrape them up. They are done when deep amber, jammy and shrunk to about a quarter. Stir in the Worcestershire sauce and set aside.

   Add in this stepButter (for the onions) 15 gOnions 200 gSalt (for the onions) 1 pinchWorcestershire sauce 1 tsp

   medium heat→medium-low heat

2. While the onions cook, stir together the mayonnaise, ketchup, mustard, chopped pickle, pickle brine, smoked paprika and garlic powder. Chill the house sauce so the flavours come together.

   Add in this stepMayonnaise 3 tbspKetchup 4 tspYellow mustard 2 tspFinely chopped dill pickle 2 tspPickle brine 1 tspSmoked paprika 2 pinchGarlic powder 1 pinch

3. Divide the beef into 70 g portions (2 per burger), roll loosely into balls and set them on a paper-lined plate in the fridge until you cook. Cold fat keeps the patty from tearing when smashed and gives a crisper crust.

   Add in this stepGround chuck (about 20% fat) 280 g

4. Butter the cut sides of the buns generously. Toast them cut side down in a 28 cm cast-iron pan over medium heat until deep golden, about 1 min in total if you work in rounds. They should be crisp on the surface and soft inside.

   Add in this stepButter (for the buns) 15 gBrioche or potato buns 2

   medium heat

5. Wipe the pan, turn the heat to high heat and heat for 3 min, until the first wisp of smoke appears. Add the tallow and let it melt.

   Add in this stepBeef tallow (or neutral oil) 1½ tsp

   high heat

6. Place 2 beef balls well apart, cover with paper and smash hard with a metal spatula to 6 mm thick and 12 cm wide, holding the pressure for 10 seconds so every bit of meat touches the pan. Peel off the paper, season with salt and coarse pepper and sear on high heat for 2 min, until the edges are lacy and deep brown. Cook in 2 batch(es) of 2.

   Add in this stepSalt 3 pinchCoarsely ground black pepper 2 pinch

   high heat

7. Scrape-flip each patty with the spatula. Put cheese on both and a spoonful of caramelized onions on one. Pour 1 tbsp water into an empty part of the pan and cover with a lid at once; steam for 30 sec so the cheese melts and drapes over the patty. Stack the onion patty on top of the plain one.

   Add in this stepSliced American cheese (or thin cheddar slices) 4Water (for melting the cheese) 2 tbsp

8. Spread house sauce on both bun halves, add pickles and the patty stack to the bottom bun and close. Wrap each burger snugly in paper and rest for 1 min: the bun softens slightly in the steam and the juices settle. Serve right away.

   Add in this stepDill pickle slices 8