Instructions

for the dough

Place flour in food processor. With processor running, add room-temperature water and process until dough forms ball and clears sides of bowl, 30 to 45 seconds. Transfer dough to counter and knead until smooth, 2 to 3 minutes. Wrap dough tightly in plastic wrap and let rest at room temperature for at least 1 hour or up to 3 hours.

for the filling

Beat eggs and ¼ teaspoon salt in small bowl until no streaks of white remain. Heat vegetable oil in 12-inch nonstick skillet over medium-high heat until just smoking. Add egg mixture and, using silicone spatula, scrape constantly and firmly along bottom of skillet until eggs are fully set and dry, 2 to 3 minutes. Transfer eggs to clean bowl and break into small (roughly ¼-inch) pieces; let cool for at least 5 minutes.
Place noodles in large bowl, cover with boiling water, and let sit until noodles are tender and translucent, 6 to 8 minutes. Drain noodles and rinse under cold running water. Drain noodles again, spread onto cutting board, and pat dry with paper towels. Chop noodles into small (roughly ¼-inch) pieces and transfer to large bowl.
Pulse mushrooms and tofu in food processor until finely chopped, 8 to 10 pulses; transfer to bowl with noodles. Fold in seitan puffs, cilantro, scallions, Sichuan peppercorn oil, sesame oil, soy sauce, ginger, white pepper, remaining ½ teaspoon salt, and cooked eggs until evenly incorporated.
Pulse cabbage in food processor until finely chopped, 8 to 10 pulses. Transfer cabbage to center of clean dish towel. Gather ends of towel and twist tightly to wring out excess moisture from cabbage. Fold cabbage into mushroom mixture until evenly combined. Use filling to stuff dumplings within 2 hours.

to roll wrappers

Unwrap dough and transfer to counter. Cut dough into 4 quarters. Working with 1 dough quarter at a time (keeping remaining quarters loosely covered with plastic), roll dough quarter into 12-inch cylinder, lightly flouring counter as needed. Slice cylinder crosswise into twelve 1-inch pieces (about ½ ounce each). Using palms of your hands, roll each piece into rough ball, then press each ball into 2-inch disk; cover with plastic.
Using small rolling pin, gently roll and press each disk into 3¼-inch round wrapper (they needn’t be perfectly round). Collect wrappers in single layer (without overlapping) on lightly floured counter; cover with plastic.

to fill dumplings

Line 2 rimmed baking sheets with parchment paper and dust lightly with flour; set aside. Working with 1 wrapper at a time (keeping remaining wrappers covered), place wrapper in palm of your nondominant hand. Spoon scant 1 tablespoon filling onto center of wrapper, then lift opposite sides of wrapper and pinch together to form small seam in center. Using your index fingers and thumbs, gently form 2 pleats along first open side, pressing gently to seal; repeat pleating and sealing on second open side. Arrange dumplings in single layer on prepared sheets.

to boil dumplings

Bring 4 quarts water to boil in large pot over high heat. Add 24 dumplings, a few at a time, stirring gently to prevent sticking. Return water to boil; boil dumplings for 15 seconds. Add 1 cup cold water, return water to boil, and boil dumplings 15 seconds longer. Repeat adding water and boiling for 15 seconds once or twice more, until dumpling dough is fully tender and filling is cooked through (entire process should take 5 to 8 minutes). Using slotted spoon or spider skimmer, transfer dumplings to serving platter.
Return water to boil and repeat boiling process with remaining dumplings. Serve dumplings hot.TO MAKE AHEAD: Freeze uncooked dumplings on baking sheets until solid. Transfer to zipper-lock bag and freeze for up to 1 month. Cook dumplings from frozen, increasing cooking time as needed until dough is fully tender and filling is cooked through.