Cut the chicken into 1 inch cubes, and toss the cubes with cornstarch to coat. Prepare all the herbs and vegetables. Divide the chopped scallions into whites and greens.
Set a wok (or large sauté pan) over high heat. Pour in the peanut oil. Add the white scallions, garlic, and ginger, Szechuan peppercorns, and Chinese chiles. Sauté for 2 minutes, then add the chicken pieces. Stir and brown for 3-5 minutes, until the chicken pieces are golden on most sides.
Add the chopped bell peppers. Stir and cook another 2 minutes.
Pour in the sherry, black bean garlic sauce, vinegar, sugar, soy sauce, and ¼ cup water. Mix and allow the sauce to simmer and thicken.
Once the sauce is thick enough to coat a spoon, stir in the peanuts and scallion greens. Turn off the heat and serve warm over rice or quinoa.