Stir fried crab with green pepper

Ingredients:
3 tablespoons cooking oil
2 tablespoons garlic 
1/2 onion, sliced
4 Thai chilies, cut in half
2 blue crabs, cleaned and cut into large pieces
1 handful green peppercorns
2 teaspoons oyster sauce
1 teaspoon sugar
2 teaspoons soy sauce
1/2 cup water or more as needed
1/2 cup Chinese celery and green onions cut into one inch length 
 
Heat the wok on high heat and stir in onion and chili; stir back and forth until fragrant, about 30 seconds. Then stir in blue crab and let it cook for 2 minutes. Stir in green peppercorn, oyster sauce, sugar and soy sauce. Stir well, then add water and let it cook until the crab is completely pink in color and the crab meat is opaque, not translucent. It takes about 3 to 5 minutes for the crab meat to cook.  Add more water in between to make a good amount of sauce but not too watery. Last, stir in Chinese celery and green onion and continue stirring for 30 seconds. Serve right away with steamed jasmine rice.