Cook the noodles in boiling water, per package directions.
While the noodles cook, heat the oil in a wok or frying pan and sauté the garlic, ginger, shallot and chili (if using) with a little salt and pepper.
Add the carrot, celery and oyster mushrooms. Sprinkle in a little more salt and pepper and stir fry for about a minute.
Drain the noodles and add to the vegetables.
Pour in the soy sauce and lemon juice. Sprinkle in the sugar. Stir fry just until blended.
Drizzle in the sesame seed oil. Toss a few more times.
Sprinkle with snipped scallions and serve at once.