To make the dough, combine the All-Purpose Flour (1 cup) and Kosher Salt (3/4 teaspoon) in a medium-sized bowl.
In a mixer with the paddle attachment or by hand, stir in the Water (1/4 cup) until the flour becomes mealy (crumbly).
Slowly add in the Water (1/4 cup) until a dough forms.
Place dough on lightly floured surface and knead 5-6 times. Place in a bowl and cover with paper towel until time for use.
To make the filling, heat about a tablespoon of Olive Oil (1 tablespoon) in a pan over medium-low heat. Add the Onion (1/4 cup) and Fresh Ginger (1 teaspoon) and cook about 2 minutes.
Add the Mushroom (1/2 cup) and Scallion (to taste) and cook 2-3 minutes until mushrooms are soft.
Add the Green Cabbage (1/2 cup) and cook another 2 minutes until the cabbage just starts to wilt. Add the remaining ingredients, stir, then reduce heat to low.
To make the potstickers, pinch off a tablespoon of dough and roll into a ball.
Using a rolling pin, roll out the dough into a 3" diameter circle on a lightly floured surface.
Spread a spoonfull of filling onto the center of the circle, then fold over one edge to the other and pinch together. Complete for remaining potstickers.
Boil a large pot of salted water. Add potstickers and cook 3-4 minutes each. You can leave as is, or transfer to a hot frying pan with oil. Cook on both sides until crispy (4 minutes).
To make the sauce, combine Soy Sauce (1 tablespoon), Rice Vinegar (1 tablespoon), Sesame Oil (to taste), Crushed Red Pepper Flakes (to taste), and Garlic Salt (to taste).
Serve with soy sauce and garnish with Scallion (to taste). Enjoy!