Make sure to use Japanese soy sauce, not Chinese, since it has a lighter flavor and won't overwhelm the Zinfandel in the marinade. Nobuo Fukuda recommends Kikkoman and Yamasa. More Incredible Duck Recipes
In a medium saucepan, boil the Zinfandel over high heat until reduced by half, about 5 minutes. Let cool to room temperature.
Bring a large pot of water to a boil. In a large, sturdy, resealable plastic freezer bag, combine the soy sauce, mirin, scallions, garlic, ginger and Zinfandel reduction.
Gather 10 bamboo skewers in your hand and puncture the duck skin all over, through to the meat. Alternatively, use the tip of a very sharp knife to poke the duck skin all over.
Heat a large skillet over high heat. Add the duck breasts, skin side down, and cook over moderate heat until deeply browned, about 8 minutes. Turn the duck over and cook until browned on the other side, about 3 minutes. Transfer the duck breasts to the bag with the marinade and seal it. Place the sealed bag inside a double layer of sturdy plastic bags, sealing each bag. Carefully lower the duck breasts into the boiling water. Cover, turn off the heat and let stand for 10 minutes.
Prepare a large bowl of ice water. Plunge the bags with the duck into the ice bath and let stand for 45 minutes, or until completely chilled. Refrigerate the duck in the bags for at least 6 hours or overnight.
Remove the duck breasts from the marinade and pat them dry with paper towels. Strain the Zinfandel marinade into a medium saucepan and boil over high heat until it has thickened, about 7 minutes. Using a thin, sharp knife, thinly slice the duck breasts crosswise. Drizzle each plate with some of the reduced Zinfandel marinade and arrange the sliced duck breasts on top. Mound the arugula leaves on the plates and serve.
The recipe can be prepared up to 3 days ahead; refrigerate the Zinfandel marinade and the cooked duck separately.