Heat vegetable oil in a large cast iron skillet over medium heat. Add mushrooms and shallots, and cook, stirring occasionally, until tender, about 3-4 minutes. Stir in cabbage and carrots until tender, about 3-5 minutes. Let cool completely.
In a large bowl, combine mushroom mixture, water chestnuts, cilantro, egg, garlic, ginger, soy sauce, rice wine vinegar and sesame oil; season with salt and pepper, to taste.
To assemble the potstickers, place wrappers on a work surface. Spoon 1 tablespoon of the mushroom mixture into the center of each wrapper.
Using your finger, rub the edges of the wrappers with water. Fold the dough over the filling to create a half-moon shape, pinching the edges to seal.
Heat remaining 2 tablespoons vegetable oil in the skillet over medium heat. Working in batches, add potstickers in a single layer and cook until beginning to crisp on the bottom, about 2-3 minutes.
Working quickly, add 1/4 cup water; cover and cook until liquid has evaporated and bottoms of dumplings are crisp and golden, about 3-5 minutes.
Serve immediately.
Notes
Let the vegetables cool. Cool the sautéed vegetables completely before assembling the potstickers. This will prevent the wrappers from becoming soggy or difficult to seal.
Use round or square wonton wrappers. Round wrappers are generally preferred for its shape but if round wrappers are not available, square wonton wrappers can also be used, folding the wrapper in half (over the filling) to form a triangle.
To pleat or not to pleat. Pleating potstickers is completely optional, and mainly done for aesthetics. As long as they are fully sealed, the filling should stay put (and taste just as delicious as the pleated potstickers!).
Work in batches. Avoid overcrowding the pan, leaving some space between each of the potstickers to brown evenly.
Serve with your favorite dipping sauce. Serve with store-bought dipping sauce (Trader Joe’s is one of my personal favorites) or a simple homemade dipping sauce consisting of soy sauce, rice wine vinegar, sesame oil, garlic, ginger and crushed red pepper flakes on top, to taste.
Keep warm. Similar to pancakes, potstickers can be kept warm in a low oven while cooking additional batches, about 200°F, covered with foil.
Freeze extra batches. Potstickers are very freezer-friendly, flash freezing once assembled (before cooking) and storing in the freezer for up to 2 months.