Put the soy curls in a bowl, cover with water and let sit for about 15 minutes, then drain well and lightly squeeze out any excess moisture.
In a heavy, shallow pot, heat about an inch of oil until hot, but not smoking. (If you have a thermometer, aim for about 175 C or 350 F.)
Fry the curls for a few minutes, until crisp; transfer with tongs or a slotted spoon to a bowl or plate. In a small bowl or measuring cup, stir the cornstarch into the cold water. Stir in the soy sauce, sugar, vinegar, ginger and chili flakes.
Set a large skillet over medium-high heat, add a drizzle of oil (use a ladle to add some of the warm oil you just cooked the soy curls in if you like) and cook the onion, pepper, carrot and garlic for a couple of minutes, until starting to soften.
Add the sauce to the pan and bring to a simmer; cook, stirring, for a couple of minutes, until thickened. Add the soy curls and toss to coat. Serve immediately, on its own or with steamed rice.