Add baking soda to beef and mix well. Let stand for 3 or 4 hours in fridge. Then soak citrus peel in warm water until soft. Drain and mince finely. (Guide Note: Dried citrus peel or dried tangerine peel can be purchased in Chinese/Asian markets. If you use fresh citrus peel, the orange flavor will be stronger.)
Pick up beef in hand and form into a large ball. Then throw the beef with some force into a large bowl 10 or so times. This makes the beef less crumbly when cooked. Alternatively, you can add a beaten egg to the mixture.
Dissolve cornstarch in cold water. Stir well and add to beef.
Add minced citrus peel, oil, white pepper, salt, chicken bouillon, sugar, sesame oil and optional egg, leaving oyster sauce until last.
Form beef balls of about 2 tablespoons of beef in your cupped hands and roll lightly.
Line a large dish with lots of watercress. Put beef balls on top. If you're using small dishes, the beef can be steamed in batches.
Steam on high heat for 8 minutes after water has come to a boil.
Serve with a soy/maggi sauce mixture.