Add 1 teaspoon sesame oil to a skillet over medium heat. Add asparagus and cook for 2-3 minutes or until asparagus is fork tender. Add 1 tablespoon soy sauce during the last minute of cooking. Remove from skillet and set aside.
Add remaining teaspoon sesame oil and add mushrooms. Cook for 2-3 minutes, adding 1 tablespoons soy sauce during the last minute. Remove from skillet and set aside.
Add remaining tablespoon soy sauce, miso paste, garlic, ginger and vegetable broth to a medium sized pot. Bring to a simmer over medium heat, stirring until miso paste dissolves.
Add udon noodles and bok choy and simmer for 2-3 minutes or until noodles are cooked. Taste broth and add more soy sauce if desired. Transfer to a bowl and garnish with scallions.