The beauty of this recipe for twice-cooked pork, brought to us by Martha's friend Lily Mei, lies in its frugality. The pork's first cooking -- simmering in water -- yields a broth that can become a flavorful soup.
Place bacon and ginger in a medium stockpot. Cover with water. Bring to a boil, skimming as necessary to remove fat. Reduce heat to simmer, and cook, covered for 40 minutes. (This can be made ahead up to this point and refrigerated overnight.) Remove bacon from liquid. Remove bones, and discard. Slice meat crosswise into slices 1/4 inch thick. Reserve liquid for Pork Broth with Tofu and Vegetables. Discard ginger.
Place wok over high heat. Add 1 1/2 tablespoons olive oil and heat until smoking. Add garlic, hot bean sauce, and sliced bacon. Cook until lightly browned, stirring frequently, about 5 minutes. Transfer from wok to plate. Rinse wok, and wipe dry.
Return wok to heat. Add remaining 1 tablespoon olive oil. Heat until smoking. Add kohlrabi and salt. Stir to combine. Add cooked meat, scallions, soy sauce, and chile oil. Cook until heated through, about 2 minutes. Remove from wok to serving dish. Drizzle with sesame oil. Serve immediately.