Slow-Cooked Black Dal

Put the urad and the kidney beans in a large bowl and cover them with cold water by at least 5cm.

Soak for 12 hours or overnight. They roughly double in size, and a pan started from dry will not soften evenly however long you give it.

Drain the pulses and rinse them well.

Tip them into a large pan with the 1.5 litres of fresh water and bring to a hard, rolling boil.

Boil hard and uncovered for 10 minutes, skimming off the foam that rises.

Do not shorten that hard boil or replace it with a gentle simmer. Dried kidney beans carry a lectin that is destroyed by ten minutes at a full boil and is not destroyed by slow cooking below it, and undercooked beans make people ill.

Turn the heat down to a steady simmer and part-cover the pan.

Cook for 1.5-2 hours, topping up with hot water from the kettle whenever the pulses come near the surface, until an urad bean crushes to cream between finger and thumb with no grit left in the middle.

Melt the 40g of butter with the oil in a wide pan over medium heat while the pulses cook.

Cook the onion for 10-12 minutes, stirring, until it is soft and deep gold at the edges.

Add the ginger, garlic and green chillies and cook for 2 minutes, until the raw smell has gone.

Stir in the cumin, coriander, turmeric and chilli powder and cook for 30-60 seconds, until they darken slightly and smell toasted. Ground spices give their flavour up to fat and burn in a dry pan, which is why they go in here rather than into the liquid later.

Add the crushed tomatoes and cook for 8-10 minutes, stirring, until the mixture has darkened and the fat separates back out around the edge of the pan.

Keep the tomatoes out until the pulses are already tender. Acid is what holds a pulse firm, and a pot that has tomato in it from the start can simmer all day without the beans ever going soft.

Tip the tomato base into the pan of cooked pulses along with all their liquid.

Stir in the 6g of fine salt.

Simmer uncovered over the lowest heat you can hold for 60-90 minutes, stirring every 15 minutes and scraping the base as you go.

Crush a ladleful of the beans against the side of the pan each time you stir, which thickens the pot without any flour.

Add hot water whenever it thickens enough to catch. A dal this dark hides a scorched base until you taste it, and burnt is the one flavour that goes all the way through.

Stop when it has gone glossy and almost black and a spoon dragged through leaves a trench that holds for a second.

Stir in the garam masala and cook for 2 minutes more. It is an aromatic blend rather than a base spice, and it goes flat if it boils for an hour.

Pour in the cream and warm it through over low heat for 2-3 minutes, without letting the pan bubble. Once dairy is in, a boil splits it into grains sitting in thin liquid.

Take the pan off the heat and stir in the cold butter until it melts and the surface turns glossy.

Taste and add salt.

Scatter over the chopped coriander.

Serve with warm flatbreads or steamed basmati rice.

Note that this is the opposite end of the same family from the weeknight red lentil dal in this collection: split lentils with the skin off collapse in half an hour, whole skin-on urad takes most of an afternoon.