This is a common street vendor food of Szechwan. The recipe for ``hot pepper flakes in oil'' is given at the end, in case you don't have any of this. Sesame paste from a Chinese grocery is best, but it's pretty good with peanut butter too. Szechwan peppercorns are also available from any Chinese grocery; if you can't find any, use a dash of freshly ground black pepper.
Smash the garlic cloves with the flat side of your cleaver, then peel.
Peel the ginger, then chop it into small pieces, about the size of a match head.
Put the garlic and ginger into a small steep-sided bowl or mortar. Add the salt and then, using the handle of your cleaver, a wooden spoon, or a pestle, mash everything together until it turns into a coarse paste. The salt helps the pulverization along, as well as bringing out the flavor of the garlic and ginger.
Add the water to the mashed garlic and ginger and stir well, so the water and the juice of the mashed ingredients are thoroughly combined.
Clean the scallions, then chop them, both green part and white, very fine, until they reach the consistency of farina; you should have about 1 Tbsp. of chopped scallions for every individual serving of noodles.
Bring a large pot of water to a rapid, rolling boil and cook the noodles according to the directions that are on the package; fresh Chinese noodles take from 5 to 10 minutes. (Test them as they cook to make sure they don't overcook and become mushy.)
Drain the noodles, rinse them in cold water, and then drain them again.
Put each individual serving of noodles on a separate plate or bowl. Then add the following ingredients to each: the garlic-ginger-water mixture, chopped scallions, hot pepper flakes in oil, ground roasted Szechwan peppercorns, sesame paste, soy sauce, and sugar. Mix very well.
For the hot pepper flakes, you can use the commercial kind as seen in pizza joints, or you can just mince any good dried red chilies.
Heat the oil until it is just beginning to smoke. Remove from heat, add the chilies, and stir. The mixture will foam and, if the chilies are the right kind, it will probably drive everyone out of the house.
This mixture can be kept for months under refrigeration.