Combine all ingredients together in a bowl; ground pork, minced shrimp, egg, chopped water chestnuts, green onions, shoyu, oyster sauce, salt, pepper, and sesame oil. Mix well.
Hold one wrapper in hand and scoop about one tablespoon of the filling on to the center of the wrapper. Bring the sides up to the top and leave it unsealed.
Place finished dumplings in a steamer basket lined with parchment paper. Over boiling water, place steamer on top and let it steam for 30 minutes. Serve it hot and enjoy!
Mustard-Shoyu Dipping Sauce:
Combine both shoyu and hot mustard in a dipping sauce bowl. Adjust the hot mustard according to taste. Enjoy!