Make the chicken marinade by mixing together the sugar, salt, soy sauce and cornflour slurry. Mix in the chicken, let marinate for 15 minutes.
Make the mushroom marinade by mixing together the sugar, soy sauce and sesame oil. Mix in the shiitake mushrooms and let marinate for 15 minutes.
Heat a large frying pan with 1 tablespoon oil over high heat. Stir-fry the chicken until done, 4-5 minutes. Set aside.
Meanwhile, make the sauce by mixing together soy sauce, black soy sauce, sugar and shaoxing wine. Set aside.
Heat the same frying pan with 1 tablespoon oil over high heat. Stir-fry the garlic, spring onions, ginger and shallots until fragrant, about 3-4 minutes. Stir in the chicken and sauce, mix well.
Add just enough hot water to cover 2/3 of the ingredients and heat through, 2-3 minutes. Stir in the chestnuts and turn down the heat to medium-low. Cover and simmer for 40 minutes. Adjust the seasoning accordingly and serve.