French onion chicken

The cook

1. 01

   Step 1TAKE YOUR TIME WITH THE ONIONS

   Choose a wide, deep, flameproof pan that will hold the flattened chicken and fit inside your BBQ with the lid closed. It must also be safe under a kitchen grill. Heat the butter and olive oil on the hob over a medium-low heat. Add the onions and a generous pinch of salt. Cook gently for 45–60 minutes, stirring regularly, until deeply golden and sweet. If they catch, add a splash of water and scrape the base. Brown and sticky is the target, not black and bitter.

2. 02

   Step 2GET THE FIRE SORTED

   While the onions cook, set up your kettle BBQ for two-zone cooking, with the coals to one side and enough space for the pan on the other. On a kamado, fit the heat deflector. Settle the temperature at 200°C with the lid closed. This is a roast, so the pan needs indirect heat.

3. 03

   Step 3BUILD THE GRAVY

   Stir the sliced garlic and thyme sprigs into the caramelised onions and cook for 1 minute. Add the flour and stir for another minute, then pour in the white wine. Scrape up all the sticky bits and simmer until the wine has reduced by roughly half, about 3–5 minutes. Add the beef stock, Worcestershire sauce, Dijon and bay leaves. Simmer for 5 minutes until slightly thickened, then taste and season.

4. 04

   Step 4FLATTEN THE BIRD

   Pat the chicken dry with kitchen paper. If it is not already spatchcocked, use sturdy poultry shears to cut down either side of the backbone and remove it. Turn the chicken breast-side up and press firmly on the breastbone to flatten it. Wash your hands and thoroughly clean the board, shears and any surfaces touched by raw chicken.

5. 05

   Step 5BUTTER UNDER, SEASONING OVER

   Mix the softened butter with the grated garlic, thyme leaves, salt and pepper. Carefully loosen the skin over the breasts and thighs with your fingers, without tearing it, then spread the butter underneath. Rub the outside with the olive oil and season generously with salt and pepper. Keeping the garlic butter under the skin protects it from burning.

6. 06

   Step 6ROAST OVER THE ONIONS

   Sit the chicken skin-side up on the onions, keeping its skin above the gravy. Put the pan over indirect heat, close the lid and roast at 200°C for approximately 45–60 minutes. Turn the pan halfway through for even colouring and add a splash of stock if the onions look dry. Check with a probe: the thickest part of the breast and the innermost thigh must both reach 75°C, without touching bone. Give it longer if needed. An oven at 200°C conventional or 180°C fan works too.

7. 07

   Step 7GET THAT CHEESE BUBBLING

   Preheat your kitchen grill to high. Scatter the Gruyère over the onions around the cooked chicken, leaving the crisp skin exposed. Slide the pan under the grill for 2–4 minutes until the cheese is melted, bubbling and golden. Keep enough clearance between the chicken and the element, and watch it constantly. Cheese goes from glorious to burnt in a heartbeat.

8. 08

   Step 8REST, CARVE, GET STUCK IN

   Rest the chicken for 10 minutes before carving, leaving it uncovered so the skin stays crisp. Remove the bay leaves and woody thyme stalks, then finish with fresh thyme leaves and black pepper. Carve and serve with buttery mash and generous spoonfuls of cheesy French onion gravy.