Wash the dhal in at least three changes of cold water until the water runs clear. Put the rinsed dhal in a large bowl with plenty of cold water, cover and leave to soak at room temperature for 12-24 hrs.

Drain and rinse the dhal, then tip into a large saucepan. Cover with 2 litres of cold water and bring to the boil, skimming any foam from the top. Turn down the heat, half-cover and gently simmer for 2 1/2-3 hrs. If the water level starts to drop below the top of the dhal, add a splash more boiling water. Once cooked, the dhal should be completely soft and start breaking down into the liquid. If the liquid is still thin, simmer for an extra few mins and mash the dhal lightly to help thicken.

Heat the oil in a small frying pan. Add the garlic and ginger and fry gently for 1-2 mins to soften but not brown. Add the ground coriander, chilli powder, turmeric and tomato purée with a large splash of water. Cook for 1-2 mins, then scrape into the pan of dhal and gently heat through.

Add extra water if needed to make the dhal looser and creamy. Sprinkle over the garam masala and remove from the heat. Serve in bowls with rice topped with a swirl of coconut yogurt, a scattering of coriander and some lime wedges on the side for squeezing over.