This recipe is adapted from ‘How To Eat’ by Nigella Lawson, who in turn adapted it from ‘an aromatic, velvety, manilla-coloured soup at Le Caprice’ in the late 1980s. The bootstrap adjustments and pricing are my own. The original recipe includes half a leek, which I have omitted out of laziness; I didn’t have one in and didn’t want to take a trip to the shop especially, but if you want to stick more closely to the original, slice it and add it at the same time as the onion. If chestnuts are a step too far outside of your comfort zone, replace with peanut butter instead; this variation benefits from a hefty whack of chilli and lemon, turning it into an entirely different meal, but a delicious one.

Serves 4-6 from 48p each. This post is not sponsored; I provide links to the ingredients that I use so you can see how I calculate my recipe costs, and I may earn a small commission if you click the links or purchase any ingredients. All prices correct at the time of printing and are subject to change.

1 small onion, 5p (54p/1kg)

1 large carrot, 6p (43p/kg)

1 stick of celery, 8p (49p/bunch)

2 tbsp oil, 3p (£1.10/1l)

200g red lentils, 36p (£1.80/kg)

1.5l vegetable stock, 3p

180g cooked chestnuts, £2.25

parsley and cream, to serve, optional

First finely chop the onion and dice the carrot, and finely slice the celery. Heat the oil in a large saucepan, and add the chopped vegetables. Cook on a low heat to allow them to soften and gently cook, for around 10 minutes.

Thoroughly rinse the red lentils under a cold tap, then add to the pan. Pour over the stock, and bring to the boil. Reduce to a simmer and continue to cook until the lentils are soft and swollen – usually around 40 minutes.

Add the chestnuts and simmer for 20 more minutes. Transfer to a blender – in batches if need be – and liquidise until smooth. Add the parsley to serve and, if feeling particularly fancy, a tablespoon of cream stirred through to finish. Milk or coconut milk will give a similar creamy effect without breaking the piggy bank!

‘How To Eat’ by Nigella Lawson is available here.

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All text copyright Jack Monroe.