Roast the duck breast over wood chips in a smoker for 10 – 15 minutes (place a pan of water under the duck to catch the drippings and prevent flare-ups). Alternatively, place over wood chips on a low fire in a covered grill for 8 – 10 minutes. Remove the skin and any remaining fat, and dice.
In a wok or large sauté pan, heat the canola oil stir-fry the diced duck meat, garlic, shallot, onions, choy sum, cilantro, gai choy (or kim chee or napa cabbage), water chestnuts, chile flakes, mushrooms, oyster sauce, mint, and basil for 5 minutes over high heat until well combined and cooked through. Drain off the liquid into a saucepan, and reduce to a syrupy consistency. Return the reduced liquid to the duck mixture, add the chile sauce and egg yolk, and mix well.
Mix 1 tablespoon of the cornstarch and the water together in a small bowl. To make the potstickers, lay out the wrappers on a work surface and place a heapin1/4 tablespoon of the filling in the center of each. Moisten the edges of the wrappers with the cornstarch mixture, fold in half, and seal the edges. Sprinkle with a little cornstarch to prevent them from sticking.
Heat the 1/4 cup canola oil in a cast-iron skillet or heavy-bottomed sauté pan. When hot, fry the potstickers over medium-high heat for about 1-1/2 minute per side, or until browned.
To serve, ladle the Orange-Chile-Plum Sauce onto warm serving plates. Place 5 potstickers on each plate in a star shape and garnish with the plum slices from the sauce, if desired, placing 1 slice between each potsticker. To garnish, place 1/2 tablespoon of the orange zest and a sprig of oregano in the center of each potsticker “star,” and sprinkle with the sesame seeds.