Whisk sherry (or rice wine), water, brown sugar, lime juice, hoisin, cornstarch and salt in a small bowl.
Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat. Add seitan; cook, stirring occasionally, until crispy, 4 to 6 minutes. Stir in the remaining 1 tablespoon oil, peanuts and ginger. Cook, stirring often, until fragrant, about 1 minute. Add carrots and bell peppers, and cook, stirring constantly, about 1 minute.
Whisk the sauce and add to the pan; stir to coat. Reduce heat to medium, cover and cook until the vegetables are crisp-tender and the sauce is thickened, 3 to 4 minutes. Stir in cilantro, if using.
Ingredient notes: The "cooking sherry" sold in many supermarkets can be surprisingly high in sodium. We prefer dry sherry, sold with other fortified wines in your wine or liquor store.Shao hsing (or Shaoxing) is a seasoned rice wine available in most Asian specialty markets and some larger supermarkets' Asian sections.Seitan is processed wheat gluten that is high in protein and has a meaty texture. It can be found in health-food stores or large supermarkets near the tofu. The actual weight of the seitan in a package varies depending on whether water weight is included. Look for the "drained weight" on the label. We used two types of White Wave seitan: one has a 1-pound 2-ounce water-packed package containing "8 ounces drained" seitan and one comes in a package labeled "8 ounces" that actually contains 8 ounces of seitan.