Bring a large pot of water to a boil. Blanch the green beans in the boiling water for two minutes, drain in a colander and plunge them in ice water to stop them from cooking any further. Set aside.In a small bowl, combine the garlic, ginger, five-spice powder, salt, and pepper. Rub the mixture onto the duck breasts and let them sit at room temperature for half an hour.Preheat the oven to 400 degrees. In a cast iron skillet, heat the olive oil over medium-high heat. Sear the duck breast, skin side down, for 5 minutes; turn and sear for 5 minutes on the other side. Transfer the pan to the oven and roast for 5 minutes for medium-rare. Transfer the duck breasts to a plate and keep warm.Pour off the fat from the pan. Return the pan to medium-high heat, add the wine or chicken stock, and stir to scrape up the browned bits from the bottom of the pan. Cook to reduce the wine by half.Add the balsamic vinegar and the trimmed green beans and cook for 3 minutes.Cut the duck breasts in half lengthwise. Slice the four halves crosswise into thin strips. Serve the sliced duck on top of the green beans and drizzle with any sauce that is left in the pan.