Tandoori chicken in a butter sauce

4 tbsp tomato purée

water, to mix

2.5cm cube of fresh ginger, peeled and grated very finely to a pulp

275ml single cream

1 tsp garam masala

¾ tsp salt

¼ tsp sugar

1 fresh, hot green chilli, finely chopped

¼ tsp cayenne pepper

1 tbsp fresh green coriander, very finely chopped

4 tsp lemon juice

1 tsp ground roasted cumin seeds

110g unsalted butter

Tandoori-style chicken