Heat 5 1/2 quart French oven over medium high heat and add cooking oil. Add scallions, garlic and ginger and sautee for 1-2 minutes, stirring constantly. Pour in vegetable broth and water. Stir. Turn up heat and bring to a boil. Reduce heat to medium low. Add carrots, mushrooms, nappa cabbage, soy sauce and crushed red pepper flakes. Stir and simmer until carrots are starting to become tender, about 5 minutes. Stir in bok choy and cook until tender about 5 more minutes.