In a food processor fitted with a metal blade, combine the egg, mustard, garlic, ginger and soy sauce. Process until smooth. Season with black pepper. With the machine running, slowly add the oils in a steady stream and process until the mixture is thick and creamy. Season with salt and pepper if necessary.
Place the Napa cabbage, red cabbage, spinach, red onions, green onions, parsley, and sugar in a large salad bowl. Mix well. Add the mayonnaise mixture to the greens and toss to mix well. Season with salt and pepper. Cover and refrigerate for at least 1 hour. Serve chilled. The slaw can be made three hours ahead.
Yield: 8 servings