Marinate chicken in sesame oil, oyster sauce, cornstarch, 1 tablespoon garlic and 1 tablespoon ginger for 30 minutes. Blanch snap peas al dente in hot salted water followed by an iced bath. Keep the peas crisp. In a hot wok, coat bottom with oil and add remaining 1 tablespoon of garlic, 1 tablespoon of ginger and white scallions. Stir quickly to avoid burning. Season chicken and brown. After about 8 minutes, add chicken stock and reduce by half. Add mushrooms quickly stir for 1 minute. Add peas just to heat up and serve. Check for seasoning. Garnish with fresh cracked black pepper. Serve with rice.