1. Pommes Mille-feulle
Preheat oven to 150°C fan-forced. Line a 20x30cm roasting dish or slice tin with baking paper.
Using a mandoline or very sharp knife, slice the potatoes into 2mm rounds. Place in a large bowl with
the melted butter, thyme, garlic, salt and pepper. Toss gently to combine. Press a third of the potato mixture into prepared tin and sprinkle with a third of the gruyere. Repeat to form three layers. Cover tightly with foil and bake for 1 hour 15 minutes until completely tender. Remove the foil and return to the oven for a further 15-20 minutes, until the top is golden brown. Allow to cool completely, then cover with baking paper and refrigerate with a weight on top for at least 2 hours, ideally overnight.
To serve, remove from tin, slice into individual portions and cook at 200°C for 12–15 minutes until heated through and the edges are crispy.

2. Brisket
Pat the brisket dry and season generously with salt and pepper. Heat the oil in a large cast iron pan or heavy-based pot over high heat. Sear the brisket on all sides until deeply golden. Remove and set aside. Reduce heat to medium-low. Add the butter to melt, then the onions, garlic, thyme and a good pinch of salt. Cook slowly, stirring every 5-10 minutes, for 45-60 minutes until the onions are deeply golden, jammy and reduced to about a quarter of their original volume. Preheat oven to 150°C fan-forced. Stir the wine into the onions, then add stock, Worcestershire sauce, mustard and bay leaves. Bring to a simmer. Return the brisket to the pot, nestling it into the onions. Cover tightly and transfer to the oven. Braise for 3.5-4 hours until completely tender and the meat pulls apart easily. Leave to rest for 30 minutes.

3. Roasted carrots
Preheat oven to 200°C. Toss the carrots with oil, salt and pepper on a roasting tray. Roast for 30 minutes, until tender.

4. Jus
Remove the brisket from the braising liquid. Using two forks, pull the meat into generous chunks. Keep warm.
Skim off the fat from the top of the braising liquid and discard. Strain liquid through a sieve into a wide saucepan, pressing the onions through to extract all the flavour. Bring to a simmer and reduce by half until thickened and glossy. Just before service, whisk in the cold diced butter. Season with salt.

5. Plating
Place an individual portion of pommes mille-feuille on a warm serving plate. Pile the pulled brisket generously beside and drizzle with jus. Add carrots and a quenelle of sour cream. Garnish with fresh chives, parsley and a pinch of sea salt. Serve with extra jus in a small jug on the side.