2 tbsp vegetable oil ,1 tbsp cumin seeds, toasted in a hot pan and crushed, 4 chicken breasts, 100g tamarind paste 250g brown sugar, 1 tbsp coriander seeds,1 tbsp cumin seeds, 1 tbsp fennel seeds, 3 green cardamom pods, small knob of fresh ginger , peeled and roughly chopped, 1 green chilli , roughly chopped - optional, large pinch of chilli powder, pinch of ground ginger, large pinch of garam masala
First make the tamarind glaze. Put all the ingredients except the ground ginger and garam masala in a medium saucepan with 500ml water. Boil for 20 minutes, stirring frequently, until reduced by about half and slightly syrupy. Strain into a bowl to remove all the spices, stir in the ground ginger and garam masala and leave to cool.
Pour half the glaze into a large bowl and set another 4 tbsp aside to serve (The rest will keep in the fridge for up to a month for a sauce or marinade.) Whisk in the oil and cumin and add the chicken. Cover and marinate in the fridge for half an hour at least - overnight is ideal.
Preheat the oven to fan 180C. Lift the chicken breasts out of the marinade and lay on a roasting tray. Roast for 30 minutes, basting with the cooking juices and the leftover marinade every 5 minutes until the chicken is lacquered and sticky.
To serve, mix the reserved glaze with 1 tablespoon water and drizzle over the chicken breasts on 4 plates. Serve with steamed rice or rice pilaf and poppadums.