Toast black peppercorns in a dry wok until they crackle and are fragrant. This will take around 3-5 minutes. Grind the peppercorns in a blender or a pestle and mortar into fine powder. Be careful as the peppercorns are very hot. Note: You can use pepper powder instead of peppercorns but the taste will not be as good.

In another wok, steam crabs for 15-20 minutes. Do not throw away the juices that the crabs released as you will be using that for later.

Add butter to a pre-heated wok (medium heat) and let it melt. Once melted, add minced garlic, shallots and curry leaves (optional) and fry till fragrant. Then add ground black pepper and fry till fragrant. Finally, add oyster sauce, sugar, and crab juices (or water) and combine well. Note: Add crab juices (or water if it's not enough) according to how watery you want the sauce to be.

Add steamed crabs into black pepper sauce and mix well.