To make siomai wrapper:
1/4 cup water
1 tablespoon vegetable or corn oil
1/4 teaspoon salt
1 1/2 cups all-purpose flour
Beat egg and mix with flour till free of lumps. Bring water, cooking oil and salt to a boil, then pour in flour. Remove from heat and beat until mixture forms a ball. Divide the dough into 1 1/4 -inch balls. Roll each ball on a floured board until paper thin. Use this to wrap your siomai. Recipe for siomai is available in this site.
You may increase your water to 1 cup if you want a thinner and more manageable dough. You may not include the egg yolk if you want a white wrapper. The yolk makes the wrapper yellowish in color.