Heat a wok or large skillet over medium-high to high heat. Swirl in 2 tablespoons of oil to the heated wok and coat the bottom. When you see wisps of white smoke, add the tofu, and stir-fry until light brown on the edges, about 2 minutes. Then add the ginger and stir-fry it until aromatic, about 30 seconds. Add all the remaining vegetables and keep them moving while searing. Don't be scared to scrape the pan and fold the vegetables over many times. Cook for about 1-2 minutes or until the Napa cabbage gets bright green and starts to soften.