In a large bowl combine the pork, cabbage, mushrooms, sesame oil, garlic, ginger, green onions, Sriracha, hoisin and black pepper. Stir until evenly mixed.
To assemble the potstickers, place one dumpling wrapper on a clean surface, lightly sprinkled with cornstarch. Keep the remaining wrappers covered with a dampened cloth so they do not dry out.
Spoon a tablespoon of the filling into the middle of the wrapper (be careful not to touch the edges with the filling as this will make it harder to seal the dumplings. You don’t want them breaking open during cooking.)
Fold the wrapper in half so that it forms a half moon shape. Starting on one end, pinch the wrapper tightly together, repeating until the dumpling is completely sealed.
Stand dumplings seam side up on a parchment paper lined baking sheet. Continue with the remaining filling and dumpling wrappers.
Once all of the dumplings are formed, place a large sauté pan with a lid over medium heat, add the vegetable oil and heat through. Arrange the potstickers in the pan in a tight circular pattern standing up in the oil, seam side up and touching one another.
Cook, uncovered, until the bottoms of the dumplings are golden brown, about 2 to 3 minutes.
Add ½ cup water to the pan, then cover tightly with a lid (do this quickly, as the liquid will splatter) and cook until most of the liquid has been absorbed and the bottoms of the dumplings are crisp and golden, about 7 minutes.
Use a spatula to remove the dumplings from the pan as they will stick to the bottom (yes, that is how they get the name “potsticker”) then place them on a plate. Serve hot with a side of soy sauce for dipping.