In a large bowl, add in vegetable stock, rice wine vinegar, mushroom seasoning, and vegan cane sugar. Stir together well. Add in soy curls and toss to combine. Let sit for 10-15 minutes to rehydrate soy curls, stirring 2-3 times while waiting.
Drain any excess liquid after 15 minutes from the bowl. Add cornstarch and shake until all the pieces are well coated (can also do this in a sealable bag).
Add the oil to a large skillet and heat over medium high. Shake off excess cornstarch and add the curls to the oil in a single layer. Do not overcrowd pan, work in batches if needed. Cook 3-4 minutes until crispy, turning to cook each side evenly. Remove from pan, set aside.
Remove all but 2 tbsp of oil. Reduce heat to medium. Add in ginger and garlic and saute for 15 seconds.
Add in water, soy sauce, brown sugar, and red pepper flakes (if adding). Let come to a boil and thicken. If you find it isn't thickening enough add 1 tablespoon of cornstarch to 1 tablespoon of cold water and stir to dissolve the cornstarch and add it to the pan.
Add the cooked soy curls back in and stir together. Let cook for 2-3 minutes or until heated through. Stirring often so the sauce doesn't burn.
Add the green onions, stir to combine everything, and cook for a final 20-30 seconds.
Remove and serve over rice or crispy rice noodles. Top with sesame seeds and more green onions if desired.