Mix all of the BBQ Sauce ingredients together in a bowl.
Preheat a large pan over medium high heat. Saute the onions in oil with a big pinch of salt for about 5 minutes, until lightly browned. Add the seitan and cook for 7 to 10 minutes, until seitan is browned. Add garlic and black pepper and saute for about a minute, until fragrant. Add a tiny bit more oil if needed.
Mix in the broccoli and cover the pan to cook, lifting intermittently to stir, until softened (about 5 minutes.)
Add the sauce, toss to coat, and cook for about 5 more minutes. Sauce should become thick and bubbly. Taste for salt and seasoning and serve!