Put the beans in a large bowl, cover with lots of cold water and leave to soak for 8 hours or overnight.

Drain the beans and tip them into a large saucepan. Cover with fresh water, bring to the boil, then reduce to a simmer and leave to bubble gently for 40 minutes or until just tender.

Meanwhile, put all the spice mix ingredients in a pan over a medium heat and cook for about 2 minutes, stirring every now and then, until toasted and fragrant. Set aside to cool, then put in a small blender or spice grinder and whizz to a powder.

Heat the oven to 140°C/120°C fan/gas 1. Put the oil in a large saucepan (one with a lid) or casserole over a medium-high heat. Add the onions and a pinch of salt, then cook for 8 minutes, stirring, until softened. Stir in the chillies, garlic and ginger, then cook for 2 minutes. Add the tomato purée and cook for another 3 minutes. Stir in the ground spice mix, passata and sugar, then bring to a simmer.

Drain the beans and add them to the sauce along with 500ml water. Stir in the lime juice and salt, then bring to a simmer. Cover with a lid and transfer to the oven. Bake for 1½ hours.

Give the beans a good stir, then return to the oven without the lid and cook for another 45-60 minutes or until the sauce has reduced and thickened. Season to taste.

When ready to serve, make the chutney by whizzing the coriander, garlic, chilli, cumin, lime zest and juice in a blender with a splash of water until smooth. Season with a little salt. Serve the beans however you like, adding a dollop each of yogurt and chutney on top.