Combine the brown bean sauce and sweet bean sauce in a small bowl, add the water, and mix well.
Heat a wok for 30 seconds, add the oil and swirl, then toss in the white part of the scallions and stir while they sizzle for a few seconds; then add the pork. Stir fry over medium heat until the pork pieces are separated. Add the water-sauce mixture and stir and toss gently over medium-low heat for about 5 minutes, or until the liquid begins to smell fragrant and the water has cooked away (when this happens, the oil will start floating up the sides). Then add the green part of the scallions. Stir only once to mix. Remove from the heat and dish out immediately into a bowl.
Boil the noodles in 4 quarts of boiling water for about 2 minutes. Drain and shake off the water.
To serve, scoop about 1 cup of cooked noodles into each of six large soup bowls and spoon 2 heaping tablespoons of sauce on top. Sprinkle the shredded garnish over the sauce and serve at once.
The meat sauce may be made ahead of time and kept in the refrigerator stored in a tightly sealed container.
Makes 6 servings for a light meal.
From Florence Lin's Complete Book of Chinese Noodles, Dumplings, and Breads.