1. Place the tamarind paste in a small bowl, add 1/2 cup boiling water. Let stand 20 minutes. Strain into a bowl through fine sieve, pressing the moisture from the paste. Discard contents of sieve. Scrape the vanilla bean into the liquid; add rice-wine vinegar, brown sugar, soy sauce, and pepper, and stir to combine. Set aside.

2. Place the wok over high heat. Add the canola oil, swirling to coat wok. Add the chicken, and cook, stirring occasionally, about 5 minutes. Add the onion, ginger, and chile, and cook, stirring constantly, until onion is transparent and chicken is lightly browned, about 3 minutes. Add the reserved tamarind mixture, and let simmer until sauce is reduced and slightly thickened and the chicken is cooked through, about 5 minutes more. Add the peaches, and cook until they are warmed through, about 1 minute more. Transfer chicken and peaches to serving bowls. Clean the wok; add bok choy, and sprinkle with 1 tablespoon water. Saute, stirring continuously, until just wilted, 1 to 2 minutes. Transfer to serving bowls. Serve garnished with fresh chile slices, scallions, and ginger.