Whisk together tapioca starch, rice flour and xanthan gum in a bowl. Add oil and 12 tablespoons of water. Mix well, adding a little bit of water at a time if necessary to form a firm, but not dry, dough. Cover bowl with plastic wrap while preparing dumpling filling. The dumpling dough can be left for several hours as long as you cover it with plastic wrap to avoid drying out.
In a bowl, mix together spinach, chicken, scallion, ginger, rice wine, soy sauce, sesame oil, salt and pepper.
Bring wrapper end together over of filling and pinch.
Repeat on other side wrapper.
Place round piece of parchment paper in Chinese steamer. Lightly oil parchment paper and place dumplings on top of parchment paper, making sure dumplings do not touch each other (otherwise, they will stick together when cooked).
Bring water to a boil in bottom pan of Chinese steamer. Place steamer pan with dumplings over boiling water, cover, reduce heat to medium-low and steam for 12-15 minutes until cooked through.
Eat immediately, or let cool, and freeze. To freeze, line a plate with plastic wrap. Gently place cooked dumplings on plate. Cover dumplings with plastic wrap and place in freezer. After dumplings are frozen, store them in a container or Ziploc bag, and keep in the freezer.
Place 1 tablespoon oil in a frying pan. Place dumplings in pan and fry until bottom of dumplings are lightly browned. Pour in 3/8 cup water and cover pan. Cook on medium, covered, until water is evaporated, about 6-8 minutes. Watch carefully as oil may sputter. After water is evaporated, continue to cook for a few minutes until bottom of dumplings are golden brown and crunchy.
Frozen steamed dumplings can be fried the same way as fresh dumplings.
The <g class="gr_ gr_190 gr-alert gr_gramm gr_run_anim Grammar multiReplace" id="190" data-gr-id="190">gluten-free</g> sauce is so versatile. Add some minced scallions or ginger if you wish. For a soy-free dipping sauce, substitute Coconut Aminos for the soy sauce.