Whisk all of the ingredients together in a small bowl. Set aside.
Steam the broccoli
Pour 1 inch of water into a large saucepan or wok and bring to a boil. Add the broccoli, cover, and steam until it's bright green and tender-crisp, about 2 minutes. Remove the broccoli from the pan, drain and set aside.
Make the General Tso's bowls
Place the cornstarch and seitan in a large plastic bag and toss well to coat.
Heat the oil in a large skillet over medium-high heat. Add the seitan cubes in a single layer. Cook for 3-5 minutes, or until crispy and golden brown on the bottoms. Gently flip and cook another 3-5 minutes on the other side. Remove the seitan from the skillet and transfer to a plate.
Add the garlic, ginger and chili peppers to the skillet. Sauté about 1 minute, until the garlic and ginger become fragrant and the chili peppers start to blacken.
Add the sauce, seitan and broccoli to skillet. Flip a few times to coat seitan pieces. Cook for about a minute, just until the sauce thickens.
Divide among bowls. Serve with rice and top with sesame seeds and scallions.
Believe it or not, this is a mild version of the dish. Increase the heat by doubling or even tripling the number of dried chilies, or adding a bit of Asian chili paste.