Oil a 900g loaf tin and line with a strip of baking parchment. Cut 1 leek into 1cm-thick slices, then use them to line the base of the tin in a single layer, fitting together snugly. Finely slice the remaining leeks.

Heat the oil in a deep frying pan, then add the finely sliced leeks and fry for 8-10 mins until softened and lightly caramelised. Add the garlic and mushrooms, then cook for another 10 mins, until the mix has dramatically reduced in size and the moisture has cooked off nicely, giving you a drier mixture.

Stir in the lemon zest and chopped sage, then season. Remove from the heat and allow to cool (spread the mixture on a plate to speed up the cooling process, if you like).

Put the chickpeas and nuts into a food processor and whizz to a coarse paste – you still want some texture in the nuts. Transfer to a bowl, then add the cooled leek mixture, cheese, egg and breadcrumbs. Mix well.

Heat the oven to 180C/160C fan/gas 4. Transfer the nut mixture to the loaf tin over the leek slices, packing it down with the back of a spoon. Cover with foil and roast for 40-45 mins, then remove the foil, turn the heat up to 200C/180C fan/gas 6 and cook for another 15-20 mins until the top is golden brown.

Allow to cool for 10 mins in the tin before inverting onto a board or serving platter and peeling off the baking parchment to reveal the leek topping. Slice and serve with carrots, greens and roast potatoes.