I got this recipe from The Book of Chinese Cooking by Jasper Spencer-Smith.
(Karen also has a post on the basic recipe for siomai here, including the recipe for the wrapper.)
3/4 pound ground pork
1/4 pound raw shelled shrimp, ground
(Believe me, I used a scale to measure these, but of course, you can approximate.)
1-1/2 tbsp soy sauce
1/2 tbsp Chinese rice wine or dry sherry
1/2 tbsp sesame oil
1/2 tbsp sugar
Dash of pepper
1 egg white
1-1/2 tsbp cornstarch
won-ton skins (I buy Nasoya brand)
green peas or chopped hard-cooked egg yolks for garnish
(Note: I usually buy pork chops then grind them using my Kitchen Aid attachment, since I can't find ground pork for sale here. I grind other ingredients as well, like the shrimp. when making lumpia, I also grind the garlic, onions, and other veggies.)
Procedure (I revised according to how I made it):
To make filling: Mix together ground pork, ground shrimp, soy sauce, rice wine or sherry, sesame oil, sugar, pepper and egg white until mixture is well blended and smoth. Stir in cornstarch. Place in a storage bag and cut one corner big enough for the content to squeeze through. Place about 1 tbsp or so of filling in the middle of wonton skin and gather the skin around the filling. Dip a teaspoon in water and use to smooth the surface of the meat.
Garnish by placing a green pea or chopped egg yolk on top of meat. Repeat with the rest of the wonton/filling. Line a steamer with a damp cloth; steam over high heat 5 minutes or until done. Serve with your fave dip (I use soy sauce/kalamansi juice as a dip. When I was in PI, I used to like it with chili paste.)
My sons love these. Also a good finger food to bring during Pinoy get-togethers.