For the chile-soy vinaigrette: Mix together the soy sauce, vinegar, sesame oil, red chiles, sesame seeds and scallions in a small bowl and set aside.
For the filling: Mix together the pork, beef, tofu, cabbage, soy sauce, sesame oil, ginger, salt, sesame seeds, sugar, black pepper, scallions and garlic in a large bowl, using your hands to really break up the tofu and to yield a very uniform texture.
Prepare your work station: Line a couple of baking sheets with wax paper and set aside. Fill a small bowl with water. Unwrap the wonton wrappers and cover lightly with a piece of plastic wrap.
Place a tablespoon of filling in the center of a wonton wrapper. Moisten the edges of the wrapper with your finger dipped in water. Fold the wrapper in half. Starting at the top of the half-circle and working towards the ends, press firmly together to seal, pressing out any air bubbles. Lay the dumpling on its side on the prepared baking sheet. Repeat assembling the dumplings with the remaining filling and wrappers, laying them in a single layer on the baking sheets.
Drizzle enough vegetable oil to cover the bottom of a large (12-inch) nonstick skillet (about 1 tablespoon) and heat over medium-high heat. Working in several batches, lay the dumplings on their sides in a single layer without crowding the pan. Cook until golden brown on both sides and the filling is cooked through, turning once, 5 to 6 minutes total (reduce the heat as needed). Alternatively, place in a steamer for about 5 to 6 minutes until cooked through. Transfer to a paper towel-lined plate to drain, then transfer to a serving platter and garnish with red chile threads. Serve with the chile-soy vinaigrette.
To test the seasoning of the filling before wrapping, cook a small patty in a little oil in a pan. Once the dumplings are assembled, you can freeze them in a single layer on their baking sheets, and then bag them up to store in the freezer.