Make a curry paste by mixing the curry powder, geera, garam masala, garlic, thyme and water in a small bowl.
In a large pot over medium high heat, add oil. When the oil is hot add curry paste and stir. Lower the heat to medium and cook for 5-7 minutes until the curry darkens.
Add onion and stir fry for 2 minutes or until the onion softens. Add pepper, water, coconut milk and salt and bring to a boil.
Add crab and cook until the sauce thickens. When the sauce is thick, turn off the stove and stir in scallion.
Tips* I used snow crab for this recipe but you can use your favorite crab. Fresh or frozen works well. I cut the snow crab legs in half and cracked the claws so that the meat will be flavored with the sauce.