To soften the dry vermicelli, soak the vermicelli in cold water for about 15 – 20 minutes. (If you're in a hurry, soak it in warm water for 5 to 10 minutes; the warmer the water, the faster it'll take to soften them.) Careful not to soak for too long, or they will be too soggy to stir-fry. With a colander, drain out the excess water.
In a pinch, I’ve also used linguine noodles. Cook them beforehand according to package instructions – cook to al dente, which is 2 minutes less than it says on package.
In a small bowl, mix together the soy sauce, rice wine, water, sugar, and pepper. Set aside.
Heat the cooking oil in a wok or large pan over medium-high heat. Stir-fry the onions, garlic, and ginger until fragrant and the onions begin to caramelize, about 1 to 2 minutes. Add half the sauce mixture. Add the vermicelli, or linguini, and then pour in the rest of the sauce. Using a pair of tongs, toss the noodles well until the vegetables and seasonings are mixed through, about 2 to 3 minutes.
If you have leftover chicken or pork, shred and add to the vermicelli mixture. Top with shredded carrots and shredded cucumber.
Make this a day ahead and serve right from the refrigerator into your child’s lunchbox.