Roughly cut 100 g Napa cabbage and julienne 30 g carrot, set it aside for the soup later. Finely chop 1 tbsp Japanese leek (naganegi) and 25 g garlic chives, prepare ½ tbsp grated ginger root and 1 clove grated garlic, and place them together on a plate for the gyoza filling.
Place 100 g ground pork in a bowl and sprinkle in ¼ tsp salt. Knead for about 1 minute until sticky.
Add the leek, garlic chives, ginger and garlic to the bowl along with 1 tsp Japanese soy sauce (koikuchi shoyu), 1 tbsp toasted sesame oil and 1 tsp sake. Lightly mix until evenly distributed.
Wrap about 1 tbsp of filling in each gyoza wrapper, making sure to seal firmly. Line them up on a tray and refrigerate for about 15 minutes.
Got leftover filling? Roll them into small meatballs and cook them in the soup so nothing gets wasted!
Pour 500 ml dashi stock into a pot and add ½ tsp sugar, 1 tbsp mirin, 1 tbsp Japanese soy sauce (koikuchi shoyu), ¼ tsp salt, and ½ tsp Chinese-style chicken bouillon powder. Give it a mix, then add the prepared napa cabbage and carrot. Heat over medium until it reaches a gentle simmer, but not boiling.
Carefully slide the gyoza in one at a time. Avoid letting them touch for the first few seconds to prevent clumping together. Bring the soup back up to a simmer, then reduce the heat to low.
Cover with a lid and gently simmer for 5 minutes, or until the gyoza float and turn slightly translucent.
Divide the soup and gyoza into bowls and sprinkle with chopped green onions, chili flakes and ground white pepper. Finish with a drizzle of toasted sesame oil, and enjoy!
Notes
*Chicken bouillon powder varies by brand. My brand is 1 tsp per 200 ml, so check the label and if yours is more concentrated (e.g., 1 tsp per 300 ml or 1 cup), use touch less to avoid oversalting, and if it's less concentrated, use a little more (and adjust to taste).Reach for soup-gyoza wrappers, not pan-fry if possible: Thin wrappers built for pan-frying tear and go limp in the broth. The thick, chewy water-gyoza kind hold through the simmer and give you a skin to bite.Hold the pot under a boil the whole time: Keep it at a lazy 85 to 95°C (185 to 203°F) where only a few bubbles break the surface. A rolling boil is likely to break the gyoza skins.Slide the dumplings in one at a time: Tip a whole batch in at once and the surface starch glues them into a lump before the skins set.Add frozen gyoza straight from the freezer, never thawed: Thawing first makes them weep and tear on the way into the pot. Drop them in frozen and give them a couple of extra minutes.