The vast majority of dry pasta/noodles are prepared by boiling water first and then adding them to the already boiling water. However, the instructions on some types of Chinese rice noodles (eg. 南昌拌粉 Nánchāng bànfěn) say to place them in a pot of cold water, bring the water to boil, and then cook for X minutes.
Is there a culinary reason for this? Or is this just a shortcut for soaking before cooking?
When cooking thinner rice noodles, due to their delicate nature, adding them to already boiling water can cause over softening. Starting from cold allows the process to be more gradual and keep them from overcooking. Thicker ones, would not require this.
This is not a complete answer, but: bear in mind that rice noodles (and mung bean noodles, etc) do not have gluten. They are held together by amylose, a form of starch. Starch absorbs water readily and can fall apart easily. My guess is that rice noodles need more delicate handling for this reason. Potatoes, which are also made of amylose, are best if started in cold water. You can put potatoes directly into boiling water, but the outer layer comes away, whereas when started in cold water the potato stays together. Harold McGee has more info on this topic. hope this little bit helps!
In addition to the overcooking or uneven cooking issue, starting noodles in cold water also prevents them from sticking or clumping together. Similar but related conversation over here. That said, in my experience, rinsing in cold water after cooking also washes away the starch, which prevents sticking, but doesn't solve the potential uneven cooking issue.
