Prepare the black pepper by pounding them with a mortar and pestle. Make sure they are slightly coarse, not powdery.

Heat up a wok with the butter. Saute the garlic and onion for 1 minute before adding the black pepper.

As soon as you smell the peppery aroma, add the crab into the wok and stir to combine well with the black pepper.

Add the oyster sauce, sugar, water and stir continuously to blend well with the crab.
Turn the heat to medium. Cover