Cut chicken into 3/4 inch pieces. Combine sherry, soy and sesame oil in a 4-cup microwaveable casserole. Toss chicken in mixture, cover and marinate while preparing other ingredients. In a small boil combine stock, cornstarch, soy sauce, sugar, chili paste; set aside. Prepare garlic, ginger and black beans; set aside. Microwave chicken and marinade, covered at high for 4 to 6 minutes or until chicken is opaque and tender. Stir twice during cooking. Stand, covered, while making sauce. In a 2 cup glass measure, microwave vegetable oil at high for 1 minute or until hot. Stir in garlic, ginger and black beans and microwave, uncovered high for 1 minute or until fragrant. Stir in stock mixture until smooth and microwave at high for 1 1/2 to 3 minutes or until sauce comes to a boil and thickens. Stir once. Drain liquid off chicken, pour black bean sauce over, stir and serve immediately.