French onion soup burger

The cook

1. 01

   Step 1SORT THE FIRE

   Light a modest bed of lumpwood charcoal in the Kamado Joe. Fit the reversible griddle flat-side up above direct heat, following your model’s fitting instructions. Stabilise the dome temperature around 200°C and let the griddle warm through for 10–15 minutes. That is the starting temperature, not the burger-searing temperature.

2. 02

   Step 2SHAPE THE BEEF

   Divide the mince into four 150 g portions. Gently shape into patties roughly 15 mm thick and slightly wider than the buns, with a shallow thumbprint in the middle. Don’t knead the mince into submission. Loose handling gives a better bite. Keep chilled until the fire is ready for them.

3. 03

   Step 3TAKE YOUR TIME WITH THE ONIONS

   Add the oil and 30 g butter to the griddle, then the onions and a small pinch of salt. Cook for 35–45 minutes, turning and scraping with a broad spatula every few minutes, closing the lid between turns. Keep the onions in a manageable layer on the plate, away from its edges. You want deep golden brown and soft, not black and crispy. If they catch early, reduce the airflow and add a tiny splash of water directly into the onions.

4. 04

   Step 4MAKE THEM SOUPY, THEN STICKY

   Stir the garlic and thyme into the onions and cook for 1 minute. Mix the stock, Worcestershire sauce and sherry vinegar. Gather the onions into a mound and add the liquid about 15 ml at a time, folding it through and letting each addition reduce before adding more. Don’t pour a puddle across the griddle. Cook for 5–8 minutes until glossy and sticky, with no loose liquid. Taste, season and transfer to a heatproof bowl. Cover to keep warm.

5. 05

   Step 5TOAST, THEN TURN IT UP

   Scrape the griddle clean. Spread the cut sides of the buns with the softened butter and toast cut-side down for 1–2 minutes until golden. Set aside. Open the vents a little and bring the dome temperature to 230–250°C. Give the griddle about 5 minutes to catch up. Burp the kamado before opening it fully.

6. 06

   Step 6BUILD THAT CRUST

   Season the patties on both sides with salt and pepper immediately before cooking. Lay them on the hot griddle with space between them; cook in two batches if your plate is tight. Cook for 3–4 minutes without moving or pressing them, then scrape underneath firmly and flip. Cook for another 2–3 minutes. The crust belongs on the burger, not stuck to the plate.

7. 07

   Step 7ONIONS ON, CHEESE ON

   Spoon the warm onions onto the patties and divide the Gruyère over the top. Close the lid for another 1–2 minutes to melt the cheese. Check each burger with an instant-read thermometer inserted sideways into the centre of the beef, not the topping. Cook until the centre reaches 75°C; allow extra time if needed.

8. 08

   Step 8GIVE THEM A BREATHER

   Transfer the burgers to a warm plate and rest for 3 minutes, leaving the cheesy tops uncovered. If cooking in batches, keep the first batch warm under a loose foil tent while the second finishes. Don’t wrap tightly or you’ll steam away that lovely crust.

9. 09

   Step 9STACK AND GET STUCK IN

   Spread Dijon over the toasted bun bases and add the sliced cornichons. Set a cheesy onion burger on each, then add the lids. The mustard and pickles cut through all that rich beef and cheese. Serve straight away, with napkins within grabbing distance.