Below the boiling water (what we Cantonese call "spaghetti"), about 10 minutes, stirring occasionally to prevent staining the pot, during which time to add a small amount of cold water twice, the purpose of doing so is to prevent the outside of the pasta is too ripe but the heart is not yet cooked. Put the noodles into cold water (preferably ice water) immediately after removing them from the pot. This is called "passing through the cold river", and the noodles will be smooth after this treatment. The next step is to stir-fry or braise as you wish.