Dissolve the bouillon cube in the hot water. Reconstitute the soy curls by placing them in a bowl and pouring the broth over them. Let them sit for about 10 minutes. Drain the soy curls, pressing out as much liquid as possible. Save the stock.
Heat 1 teaspoon of oil in large pan or skillet over medium high heat. Add the soy curls along with 1 tablespoon of tamari and 1 tablespoon of rice vinegar. Cook, stirring frequently, until they begin to brown, about 5 to 10 minutes. If they begin to stick use some of the reserved broth to moisten the pan. Once the soy curls have browned to your liking, remove them from the pan and set aside.
While the soy curls are cooking, mix together 1 cup of the reserved broth with the sesame oil, garlic chili sauce, garlic, ginger, cornstarch, and remaining tamari and rice vinegar. Set aside.
Add the rest of the oil to the pan along with the onion and mushrooms and cook for about 5 minutes, until they begin to brown and are fragrant. Add the broccoli and shredded carrot. Cook, stirring frequently, for just a few minutes, until the broccoli turns bright green. Add the soy curls back into the pan along with the sauce and mix together to heated throughout, another minute or two.
Serve with rice, and top with sesame seeds, sliced scallions, and sriracha, if using.