Cover 2 tbsp dried wood ear mushroom with boiling water and soak for about 20 minutes.Wrap 100 g firm tofu in paper towels and heat it in the microwave at 600W for 2 to 3 minutes. Once it is cool enough to hold, give it a light squeeze.
Cut just the hard end off the stems of 50 g fresh shiitake mushroom, then tear the mushrooms, stems included, into bite-size pieces with your hands. Coarsely chop 50 g canned bamboo shoots and roughly chop 30 g garlic chives.When the thick middle of the wood ear feels soft, drain it. Trim away the hard stub at the base and chop the rest coarsely.
Put the drained tofu in a bowl with 1 tbsp yellow miso paste (awase), ½ tbsp Japanese soy sauce (koikuchi shoyu) and 1 tsp sake, then mix.
Add the shiitake, bamboo shoots, wood ear, garlic chives, ¼ tsp sugar and 1 tsp mirin, and mix just until it all looks even. Add ½ tbsp grated garlic, 1 tsp grated ginger root and 1 tbsp toasted sesame oil and fold everything together.
Just before you start wrapping, add 1 tbsp potato starch (katakuriko) and mix lightly until the filling holds together. Working with 20 gyoza wrappers one at a time, lay a wrapper on your palm and spoon ½ to 1 tbsp of filling into the middle, leaving a little room around the edge.
Dab a little water along the edge, fold the wrapper in half and seal it, pleating one side 5 to 6 times as you go. Tap the bottom of each gyoza lightly to flatten it.
Heat a frying pan over medium heat, add ½ tsp cooking oil and arrange the gyoza smooth side down in a single layer. Fry until the bottoms are golden brown and crisp.
Prepare 3 tbsp freshly boiled water and pour it into the pan right away. Cover with a lid and steam until almost no water is left, 4 to 6 minutes.
While the gyoza steam, stir together 1 tbsp unseasoned rice vinegar (komezu), 2 tsp Japanese soy sauce (koikuchi shoyu) and ½ tsp chili oil (rayu) for the dipping sauce.
Take off the lid and cook off any remaining water. Drizzle about 1 tsp toasted sesame oil down the sides of the pan and fry until the bottoms are crisp again. Cover the pan with a plate, turn the gyoza out onto it, sprinkle with 1 pinch ground black pepper and serve with the dipping sauce. Enjoy!
Notes
If the filling looks wet: Water pools in the bowl, or a spoonful of filling spreads and will not hold its shape. Either way, work in potato starch a little at a time before you wrap, until the filling holds together.Always press the tofu: Tofu that still holds its water loosens the filling, turns the wrappers soggy and keeps the wings from forming well.Add the starch right before you wrap: Mixed filling keeps giving up water from the tofu and vegetables the longer it sits. Starch added early soaks up that water and stops binding. Wrap all of the filling on the day you mix it.Season the tofu first, add the sesame oil last: Work the miso, soy sauce and sake into the tofu on its own first. Added at the very end, the sesame oil keeps its aroma.Steam with boiling water: Cold water drops the temperature of the pan, and the wrappers turn soggy.Flip onto a plate only once the pan is dry: Flipping early can result in soggy gyoza that tear easily. The water should be completely gone before trying to remove them from the pan.