Halve the onion and the pepper, then add half of each to a food processor along with the garlic, ginger, one of the chillies, tomato puree and half of the garam masala and turmeric. Add a dash of oil and then blitz into a thick paste

Melt the butter in a frying pan with a dash of oil and add the cumin and mustard seeds. Slice the remaining onion and pepper and fry for 5 minutes along with the diced chicken and half the curry leaves.

Stir in the paste and fry for a further five minutes, then add the boiling water, the remaining curry leaves, garam masala and half the coriander. Deseed and chop the remaining chillies, then add half to the curry. Bring to the boil, then turn the heat down and simmer for 20 minutes, until the curry has thickened. Season with salt, to taste

Stir in the double cream and then turn off the heat. Garnish with the remaining coriander and chillies and serve with boiled rice or naan.