Season the duck breasts with Hawaiian salt and pepper. Score the fat of the skin in a criss-cross pattern. Heat a large saute pan over high heat. Add the seasoned duck breast, skin-side down, and cook until the fat is golden brown and a lot of the fat is rendered. Turn over and cook until the meat is medium rare. Remove the duck from the pan. Reserve 3 tablespoons of the duck fat.
Bring a large pot of salted water to a boil. Add the noodles and cook until just al dente. Drain and rinse under cold running water. Drain well.
Heat a wok over high heat. When hot, add 2 tablespoons of the duck fat and swirl to coat the sides and bottom of the wok. Add the green onions, ginger and garlic and stir-fry until aromatic, 30 seconds. Add the bok choy and carrots and stir-fry until tender, 1 to 2 minutes. Deglaze the pan with the coffee and add the soy sauce and oyster sauce. Add the noodles and macadamia nuts and toss well. Place the noodles in a large platter or bowl. Slice the duck breasts on the bias into thin slices. Fan the duck over the noodles. Garnish with mung bean sprouts.
