1. In a mixing bowl, combine soy sauce, oyster sauce, five-spice powder, white pepper, and minced garlic. Add chicken pieces and mix well. Marinate for at least 2 hours or overnight for best results.
2. Heat oil in a deep fryer or large pot to 350°F (175°C).
3. Dredge marinated chicken pieces in cornstarch, ensuring they are well-coated.
4. Fry chicken pieces in batches until golden brown and crispy, about 10-12 minutes per batch. Drain on paper towels.