Heat sesame oil in large skillet over medium heat.
Cook ginger for about 30 seconds, add mushrooms and cook for 2 to 3 minutes, stirring constantly.
Add leeks, scallions, water chestnuts, tamari soy sauce and cook for 30 seconds, stirring constantly.
Mince tofu in food processor. Add to mushroom mixture. Cool for 10 minutes.
Line cookie sheet with parchment paper and dust with cornstarch.
To assemble, place wrapper on work surface; keep unused wrappers under plastic wrap. Put 2 to 3 tablespoons filling in middle. Moisten edges of wrapper with water. Fold wrapper in half over filling, pinching shut at center.
Starting on right side of sealed edge and working towards midpoint, pinch small pleats in wrapper edges.
Repeat from left side. Put pot sticker on cookie sheet. Repeat with remaining ingredients.