Heat the oil in a large skillet and sauté the onions for 3 to 4 minutes. Add the celery and seitan. Sauté another 5 minutes. Place the bread, sautéed vegetables and all remaining ingredients, except the mushrooms, parsley and paprika, in a bowl and mix thoroughly.
Preheat the oven to 350° while you stuff the mushrooms. Fill each mushroom with equal amounts of stuffing and sprinkle the parsley and paprika on top. Lightly oil a baking sheet and place the stuffed mushroom on it. Bake for 20 to 25 minutes until tender and juicy. Remove and serve 3 mushroom per person.
The mushrooms can be broiled for 7 minutes or so instead of baked, if desired.
Per serving - 268 calories, 11 g fat (36% calories from fat), 10 g protein, 35 g carbohydrate, 5 g fiber, 0 mg cholesterol, 446 mg sodium