Step 1

Set a large cast-iron casserole or saucepan over a medium heat. Divide the beef mince into 3 and add the first 1 / 3 to the pan. Use a wooden spoon to break it up, then fry for 2-3 minutes, until nicely golden all over. Caramelisation will add flavour, so don’t be afraid to let it start colouring. Use a slotted spoon to remove the cooked mince and put into a bowl, before repeating with the rest of the meat.

Step 2

Add the olive oil to the pan (leaving any excess beef fat and brown bits in the pan), then add the onion, carrot and celery. Sauté for 5-8 minutes, until beginning to soften.

Step 3

Blitz the mushrooms in a mini chopper or food processor (or finely chop by hand) until they resemble rough breadcrumbs. Add to the pan and cook for a further 3-4 minutes. Add the tomato purée and stir well.

Step 4

Pour in the wine and scrape the bottom of the pan with the spoon to release its flavour into the sauce. After cooking for 1 minute, add the browned mince back in, along with the stock, Marmite, Worcestershire sauce and bay leaf. Put the lid on the pan and simmer for 10 minutes, while you prepare the mash.

Step 5

Preheat the oven to 200ºC, gas mark 6. Peel and chop the potatoes into even-sized pieces, each roughly the size of a golf ball. Add to a large saucepan and cover with cold water. Bring to the boil and cook for 10-15 minutes, until the potatoes are tender when pierced with a knife. Drain into a colander, then rinse the potatoes in cold water (to wash away excess starch that makes the mash gluey) and set aside.

Step 6

Remove the lid from the mince and allow to reduce for a further 5-10 minutes. Pass the potatoes through a potato ricer (see tips) back into the saucepan and add 75g butter and the milk. Stir just enough to combine and season.

Step 7

Taste the mince and season. Remove the bay leaf and pour into a 2L ovenproof dish (about 20x25cm). Spread the mashed potato over the top of the mince and use the back of a spoon to create a wavy texture in the potato. Sprinkle with the grated cheese and dot over the remaining 15g butter. Bake for 25-30 minutes, or until the potato is golden brown on top and piping hot throughout. Allow to stand for 5 minutes before serving with green veg.