Beef fillet with pressed potato, leeks and horseradish emulsion

The potatoes, beef and sauce are all best if made a day in advance. For the pressed potatoes, place a large pan over a medium heat and add the butter. Once melted, add the onions with a pinch of salt and the thyme and cook until soft and golden – this will take at least 10 minutes

Preheat an oven to 180ºC/gas mark 4 and line a 20x15cm terrine mould with baking paper

Peel and very finely slice the potatoes (use a mandoline if you have one). Place the potatoes neatly into the terrine mould in layers. After the first two layers, alternate with a layer of the cooked onion. Season between each layer and ensure the final top layer is potatoes. Cover with a sheet of baking paper followed by a layer of tin foil and cook for 40 minutes, or until completely cooked through when a knife is inserted

While the terrine bakes, neaten and trim the beef fillet of any sinew, saving any trimmings for the sauce. Place the fillet on some cling film and lightly cover the whole thing with the yeast flakes. Roll the beef in the clingfilm as tight as possible and tie both ends. Store in the fridge overnight

Once the terrine is cooked through, remove the tin foil and place something heavy on top of the potatoes. Place in the fridge to chill and set overnight

To make the sauce, place a large stockpot over a medium heat with a splash of vegetable oil. Roughly chop the green parts of the leeks (reserving the white ends) and add them to the pan with the carrots, onions and beef trimmings. Add a pinch of salt and cook until soft and caramelised (around 10 minutes)

Add the sherry vinegar and leave to bubble and reduce for 5 minutes, then add the red wine and bring back to the boil. Leave to simmer for around 20 minutes, then pour in the stock and bring to a simmer, skimming off any foam on the surface. Simmer for 2 hours

After 2 hours, strain the sauce through a fine sieve into a clean pan and simmer until reduced to a sauce consistency (around 1 hour). Place in the fridge ready to reheat before serving

The next day, make the braised leeks. Preheat the oven to 180ºC/gas mark 4

Place the reserved white parts of the leeks in a baking dish with the stock, butter, bay leaves, mustard and vinegar with a pinch of salt. Cover with a sheet of baking paper followed by a sheet of of tin foil and cook for 25 minutes or until tender but still holding their shape

While the leeks bake, make the horseradish emulsion. Whisk the yolk, mustard, vinegar and horseradish for a minute or so, until thick and pale. Slowly drizzle in the oil whilst continuously whisking to create an emulsion. If it begins to split, add a dash of cold water to bring it back together again. Taste, season and transfer to a piping bag

Remove the leeks from the cooking liquor and leave to cool. Pour the cooking liquor into a small saucepan and simmer over a medium heat until it thickens into a glaze. Once the leeks have cooled, halve them lengthways and place on an ovenproof tray. Set aside with the glaze ready to finish off under the grill before serving

Turn out the set potato terrine and carefully carve into thick slices. Ensure the oven remains on at 180°C/gas mark 4

To cook the beef, unwrap it from the clingfilm, patting the meat dry with some kitchen paper. Place an ovenproof frying pan over a high heat and, once smoking hot, add the fillet. Sear well on all sides, then add the butter, garlic and thyme and baste the fillet all over for a minute or so. Transfer the pan to the oven for 8-12 minutes, depending on the thickness of the fillet. At the same time, place the slices of potato terrine in the oven to warm through as well

While the beef cooks, gently reheat the sauce and preheat a grill to high. Once the beef is ready, leave it to rest for 5 minutes. Meanwhile, brush the cut sides of the leeks liberally with the glaze and place them cut-side up under the grill to reheat and blister

To serve, carve the beef fillet into 4 thick slices and place them cut-side up on the plate, sprinkling them with sea salt. Place the potato terrine and leek beside it. Pipe a blob of emulsion onto the plate, sprinkled with finely chopped chives, then spoon over the sauce