The ox tongue needs brining for 3 days, so begin here. Put all of the ingredients, except the ox tongue, into a saucepan and bring to the boil. Remove from the heat and leave to cool. Once cooled, pass through a fine sieve to remove the aromatics. Submerge the tongue in the brine and refrigerate for 3 days

Remove the tongue from the brine and place into a large vacuum pac bag and fully seal. Cook in a water bath for 48 hours at 63°C. If you don’t have sous vide equipment, you can cook the tongue in a pan. Place in a large saucepan and cover with water. Bring to the boil, skimming off the scum that rises to the surface. Once the water is boiling, cook for 3-4 hours or until a knife pierces the thickest part of the tongue without resistance

Once cooked, leave to cool slightly, then when able to handle, peel the skin off the tongue (this only comes off easily when warm so don’t let it cool completely)

Place the tongue onto a tray lined with baking paper and place another tray on top, weighted down with tins. Leave to set in the fridge overnight

Next make the beef stock – this can also be made several days in advance and kept in the fridge. Preheat an oven to 220°C/gas mark 9. Spread the bones over two trays and roast in the oven for 45 minutes until caramelised. Meanwhile, slowly sweat down the onions, carrots, celery and garlic in a splash of oil until deeply caramelised. Add the wine and reduce until syrupy

Set aside 250g of the roasted bones for later, then place the rest in the pan with the vegetables along with the stock. Bring to the boil, then skim and turn down to a simmer. Add the tomatoes and mushrooms and simmer for 2 hours, skimming regularly. Season to taste, then pass the stock through a fine sieve and into a clean pan

Now the beef stock is made, you can braise the cheeks in it. Place a large pan over a high heat and, once smoking, add the cheeks with a touch of vegetable oil. Caramelise all over then remove from the pan and turn down the heat to medium

Add the onion, garlic and carrot and caramelise for 5 minutes, then add the wine, bay leaf and peppercorns, and simmer until reduced by two-thirds. Add the cheeks back into the pan and cover with 300ml of the beef stock (or enough until covered). Place a lid on the pan and cook for 3-4 hours until tender (topping up with stock if needed)

Pour the remaining beef stock into a saucepan. Add the reduced veal stock and reduce at a rolling boil until a very thick, almost syrupy consistency is reached. Refresh with the 250g of reserved beef bones and let it sit off the heat for 30 minutes, then taste for seasoning and pass through a fine sieve into a suitable container. Reserve in the fridge until ready to use – it should be thick and almost solid once it’s chilled

To cook the Roscoff onions, carefully peel the onions but keep the root intact, so they are whole and keep their shape. Place them in a saucepan and cover with beef fat, then place over a low heat and gently confit for 1-2 hours, or until the onions are very soft and tender

Once soft and cooked through, lift the onions out of the fat and leave until cool enough to handle. Trim off the root and carefully remove the inside of 6 of the cooked onions, so you have the outer shell whole and intact. Place these shells to one side, ready to stuff with the ox cheek. Divide the remaining 2 onions into petals and chop the removed insides up, ready to include in the purée

To make the purée, heat the beef fat in a pan and caramelise the chopped onion insides and garlic with the herbs until soft and golden. Once reduced, add the cream and chicken stock, bring to a simmer and reduce by half. Add the Parmesan and season, then take off the heat. Remove all the herbs and blend until smooth, then season, pass through a fine sieve and set aside

Now you are ready to cook the steaks. Heat 2 large frying pans until smoking hot (or use a plancha if you have one available) and season the steaks generously with salt. Once smoking, add some beef fat to the pan, followed by the steaks. Cook for 2 minutes on each side then leave to rest while preparing the final elements. Gently reheat the puree and sauce, and get everything else ready in front of you

Finely slice the beef tongue on a meat slicer or using a very sharp knife, until you have 18 neat slices. Finely dice the remaining ox tongue and add to the pan of sauce

Take the onion skins and carefully stuff with the cooked ox cheek meat. Place them in a pan with a little of the beef sauce and gently heat, using a spoon to glaze the onions with the sauce, and continue to cook until warmed through. Carefully decorate each onion with thyme leaves

Place the steaks back on the heat for another minute and rest once more before carving

To serve, add 2 spoonfuls of the puree onto each plate along with an ox cheek onion. Add rolled up slices of ox tongue and the reserved beef fat onion petals. Carve each steak into 4 and add 2 slices to each plate. Finish by spooning over the beef sauce and finish with the fennel pollen, wood sorrel and mustard frills