Soak 250g of yellow split peas in cold water overnight (or put them in first thing in the morning for the evening). Drain them, tip them into a saucepan and cover with cold water. Bring to the boil, then cook for about 20-25 minutes until tender enough to crush. Add a little salt about 15 minutes after they have come to the boil. Make a herb paste: toast 80g of cashews in a dry, shallow pan until golden. Tip them into the bowl of a food processor, add 50g of coriander leaves and stalks, and 50g of basil and process to a rough paste. Mix in 4 tbsp of freshly squeezed lime juice. While the split peas are cooking, peel and roughly chop 1 medium-sized onion and finely slice 3 cloves of garlic. Warm 2 tbsp of groundnut or vegetable oil in a medium-sized saucepan, add the onion and garlic and cook over a moderate heat for 10 minutes, stirring regularly, until soft and translucent. Stir 1 tsp each of ground turmeric and paprika into the onions, then roughly chop and add 500g of tomatoes. Let the mixture cook, on low heat, for about 15 minutes, then stir in the drained, cooked split peas, 200ml of their cooking water and 5 tbsp of the herb paste. Stir well and bring to the boil, then ladle into bowls. For a particularly velvety texture, remove a third of the mixture with a ladle and process briefly in a food mixer, then stir back into the cooked split peas. There may be some spare herb paste. It will keep in the fridge, in fine condition, for several days in a stoppered jar. You can use it for pasta. Follow Nigel on Twitter @NigelSlater As a reader of the Guardian’s food journalism, we’d love to hear from you. Participate in our survey for a chance to win a Feast apron and mug, or a Guardian tote bag. Take the survey here.