Score the plantains by cutting a long line through the peel from tip to tip. Microwave the plantains for 7 minutes. (The peels with turn black in the microwave.)
Carefully remove the peels and place the plantain flesh in a food processor. Discard the peels. Add the salt, then cover the food processor and turn on high until the plantains chop into tiny pieces and eventually form a tight ball of dough. This takes a few minutes, so don't worry if it looks like it's not coming together.
Add the pork, egg, water chestnuts, green onions, coconut aminos, mustard, ginger, and garlic to a medium mixing bowl. Add 1/4 teaspoon salt and 1/4 teaspoon black pepper. Mix thoroughly by hand until the mixture is smooth.
Place a piece of plastic wrap on the counter and smooth it flat. Then use a 2-teaspoon sized cookie scoop to measure out the dough. Roll each portion into a tight ball.
Place one plantain dough ball on the plastic and cover it with another piece of plastic. Roll the dough out into a flat 3-inch circle. It's okay if it's not perfect.
Measure 1 teaspoon of the ground pork mixture onto the circle. Pinch the top of the circle up over the pork. Then starting on one side, fold small pleats toward the middle and pinch them together, until the dumpling is completely closed. Repeat until you use up all the dough and pork mixture.
Once all the dumplings are made, heat a large nonstick skillet over medium-low heat. Add 1 tablespoon sesame oil. Once hot, add half the dumplings to the skillet. Brown the dumplings on three sides, cooking for about 5-6 minutes total. Remove the dumplings, then repeat with the remaining oil and dumplings. Serve warm as-is or with dipping sauce.
After each batch of dumplings cooks, check one dumpling to make sure the pork has cooked through.
If you don't like the idea of microwaving your food, you can cut the plantains in large chunks and boil them in water for 25 minutes. Then drain off the water, peel the chunks, and proceed with the recipe.
After several test batches of this recipe, we noticed one batch of green plantains was too moist for some reason, and would not form into a ball. We decided to let it rest for 20 minutes, then try processing it again. This gave the dough just enough time to dry out, and it balled right up for the perfect texture.