Preheat the oven to 200°C.
Mix all crab ingredients except the crabs into a paste in a bowl.
Coat the crabs gently in the paste and marinate for 30 minutes if possible.
Fry crabs in an ovenproof pan with oil for 2-3 minutes per side.
Transfer the pan to the oven and cook for 8-10 minutes until cooked through.
Toast the chutney spices in a hot frying pan for 30 seconds.
Add sliced green and ripe mangoes and cook for 1-2 minutes.
Dissolve sugar into the juices and stir in the vinegar.
Cover and simmer the mixture for 25 minutes until the mango breaks down.
Puree half of the mixture in a food processor and stir back into the pan.
Cool the chutney in jars and serve alongside the crabs.