Slivered Seitan and Vegetable Stir Fry

1/3 C water
3 T rice vinegar
2 T light brown sugar
1/4 C soy sauce
1 1/2 t tomato paste
2 T minced garlic
1 T grated fresh ginger
1/2 t dry mustard
1/2 t hot red pepper flakes
2 T hoisin sauce
1 t cornstarch dissolved in 1 tablespoon water
2 T canola oil
1 - yellow onion, thinly sliced
1 - green bell pepper, cut into thin strips
1 - red bell pepper, cut into thin strips
8 oz. broccoli florets, blanched
8 oz. seitan, cut into thin slivers
1/2 C canned water chestnuts, drained and rinsed

In a saucepan, combine the water, vinegar, sugar, soy sauce, tomato paste, garlic, ginger, mustard, hot red pepper flakes, and hoisin sauce, and bring to a boil, stirring until well mixed. Reduce the heat to medium and simmer for 10 minutes, stirring occasionally to prevent sticking. Stir in the cornstarch mixture and simmer until the sauce is thickened and translucent. Set aside.

In a large skillet or wok, heat the oil over medium-high heat. Add the onion and bell peppers, and stir fry for about 2 minutes. Add the broccoli and stir fry until crisp tender, about 3 minutes. Add the seitan and water chestnuts, and stir fry until the seitan is browned, about 5 minutes longer. Stir in the sauce and stir fry until the seitan and vegetables are coated.

From Vegan Fire and Spice