Roast the duck breast over wood chips in a smoker for 10 to 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 to 10 minutes.
Remove the skin and any remaining fat and dice.
In a wok or large saute pan, heat the canola oil and stir-fry the diced duck meat, garlic, shallot, onions, choy sum, cilantro, gai choy (or kimchee 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 heaping 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 saute pan.
When hot, fry the potstickers over medium-high heat for about 1-1/2 minutes 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.
Combine all the ingredients except plums in a saucepan, reduce the heat to low and simmer for 10 to 15 minutes until thickened.
Strain and return to a clean saucepan.
Add sliced plums and simmer for 5 minutes over very low heat.
Strain before serving. (If suitable, the plum slices can be used as garnish).