If you're opposed to frying, you could bake the soy curls instead until they're crisp, they just won't be the same level of crispy. It'll still be tasty but not quite the same. If you don't want to fry or bake that crispiness at all, you could omit the cornstarch step altogether and just add the soy curls directly to the sauce, but it will be very soft. Still tasty, but the texture won't be the same (and the texture is kind of what makes this dish so wildly good).