Place chicken into a shallow dish. Mix yogurt, garlic, cumin, coriander & chilli in a bowl. Pour over chicken. Coat well.
Cover with plastic wrap. Marinate in the fridge for at least 1 hour, but is better overnight.
Remove excess yogurt mixture from chicken & set aside. Arrange drumsticks on a foil-lined baking tray. Bake in a moderately hot oven (400F)for 35 - 45 minutes or until cooked, will depend on your oven and the size of the drumsticks.
Place reserved yogurt mixture into a saucepan. Blend in cornflour & sugar. Bring to the boil, stirring continuously. Reduce heat to a moderate simmer for 3 minutes.
Serve chicken with rice and peas. Drizzle with sauce. Accompany with other vegetables or salad.