Cut cabbage, carrots, celery and scallion in strips.
Heat oil in a deep pan. Add vegetables and stir-fry until they begin to soften (2 to 3 minutes).
Add water, soy Sauce, sherry, salt and pepper. Bring to a boil, then simmer, covered, 10 minutes.
NOTE: This soup is always made with plain water, never meat stock.
VARIATIONS: For the vegetables, substitute 1/2 cup fresh mushrooms, sliced; and 1 Cup spinach, cut in 1-inch sections. Stir-fry the mushrooms 3 minutes, the spinach 1 to 2 minutes; then simmer, uncovered, 2 minutes.
For the vegetables, substitute 1/4 cup mushrooms, 1/4 cup water chestnuts, 1/4 cup bamboo shoots, 1/8 cup onions, 1 tomato, 1/4 cup Chinese white turnip, and 1/4 cup pickled mustard cabbage, all diced. Stir-fry 5 to 6 minutes. Simmer as in step 3.