If you have time, put the beef in a large bowl, pour over the wine and chill for 24 hrs before making the pie. Drain. Dry the beef well using kitchen paper, reserving the wine.

Heat the oven to 160C/140C fan/gas 3. Heat 1 tbsp of the oil in a large flameproof casserole dish and brown the beef well in batches, then remove to a plate. Tip the onions into the casserole dish along with the carrots and a drizzle of oil, then cook over a low heat for 5 mins until coloured. Scatter in the flour, stirring until it turns light brown. Add the ketchup.

Stir the beef and any juices back into the pan. Pour in the wine, simmer for 5 mins, then pour in the stock. Set aside 1 tsp thyme leaves, then tie the remaining sprigs with the bay using kitchen string, add to the pan, season and bring to a simmer. Cover with a lid and put in the oven for 2 hrs-2 hrs 30 mins, or until the beef is tender (this will depend on the cut). Cool completely – the pie will be better if the filling is fridge-cold. Will keep chilled for two days, or frozen for up to three months.

To make the pastry, mix the flour, mustard powder and butter with a large pinch of sea salt in a large bowl, then slowly add up to 250ml ice-cold water, mixing to make a soft dough. (You can use a food processor if you like.) Knead the 1 tsp thyme leaves into the pastry, then cover and chill for at least 1 hr. Will keep chilled for two days or frozen for up to a month.

Tip the potatoes into a pan of cold salted water, bring to the boil, simmer for 2 mins, then drain. While they’re hot, toss through the butter and set aside. Heat the oven to 220C/200C fan/gas 7 with a baking tray inside. Generously butter a 26-28cm pie dish and dust with flour. Cut off a third of the pastry and set aside. Roll out the remaining pastry to a thick round that will line the pie dish with an overhang, then line the tin. Tip in the potatoes so they cover the base, then add the beef. The filling should be slightly higher than the rim of the dish. Brush the edges with egg yolk. Roll out the remaining pastry to a thick round large enough to cover the pie, then lift onto the pie dish. Trim the edges and crimp together. Brush the top with more of the egg yolk, season with sea salt and cut a hole in the centre using a knife. Put it on the hot baking tray and bake for 40-45 mins until golden. Leave to rest for 10 mins before slicing.