Hang the curd in a fine muslin cloth for an hour. In a bowl mix together curd, garlic, ginger, green chilli paste, garam masala powder, coriander powder, cumin seed powder, red chilli powder, lemon juice, oil and salt.
Marinate the crabs in the curd mixture.
Keep covered in the fridge for at least 2 hours.
Pre-heat the oven. Place the crabs in an oven proof dish.
Cover with an aluminium foil.
Grill at 180 degree C for 10 minutes.
Check to see if the crabs are done.
Just before serving open the aluminium foil and grill uncovered for 4 to 5 minutes.
The curd mixture on the crabs should be fairly dry. Serve hot.