In a large saucepan over medium heat, add your seitan and saute just until it starts to crisp up, about 5 minutes, stirring frequently. (You can also use cubed tofu or tempeh for this step instead - but it will alter the macros)
Add broth paste, water, soy sauce, brown sugar, sesame oil, sriracha, garlic, and green onions to the pot. Cook for 5-7 minutes until it is a low boil.
Take about 1/3 c of the liquid out of the pot and whisk the cornstarch into it. Add this mixture back to the pot and stir it in to coat.
Add the broccoli to the pot and stir it in well. Cook for an additional 5-7 minutes until the broccoli is cooked to desired doneness.
Garnish with sesame seeds and green onions if desired.