In a bowl, toss the tofu with cornstarch, drizzle with oil, season with salt and pepper.
In a large skillet, heat the oil over medium heat. Add the tofu. Cook until both sides are lightly golden, about 6 min. Remove from the skillet and set aside.
Meanwhile, prepare the sauce. In a bowl, combine all ingredients.
In a large skillet, heat the oil over medium-high heat. Add all veggies. Cook, stirring, about 4-5 min.
Add the sauce and combine with veggies. Then add the tofu, carefully combine. Cook until the sauce thickened, about 3-4 min. Veggies should be crispy.
Sprinkle with spring onions (optional).