Make the marinade by mixing together the sugar, salt, soy sauce and cornflour slurry. Mix in the chicken, let marinate for 15 minutes.
In a small bowl, mix together oyster sauce, sugar and sesame oil to make the sauce. Set aside.
Heat a large frying pan with 1 tablespoon oil over high heat. Stir-fry the garlic and ginger until fragrant, 2-3 minutes. Stir in the onion and salt and fry until soft, 3-4 minutes. Add the chicken, stir-fry until all sides are evenly browned, 3-4 minutes. Stir in the pioppino mushrooms and black fungus, stir to mix.
Add in 1/2 tablespoon water and allow to heat through, 1-2 minutes. Reduce the heat to medium and simmer for 5 minutes or until the chicken is fully cooked. Stir in the sauce and mix to combine, serve hot
Pioppino are a type of Japanese mushroom. They are also known as black poplar mushrooms and shimeji.
Black fungus are also known as wood ear mushrooms.
You will find both types of mushrooms in Chinese/Oriental speciality stores.
If you'd like a thicker sauce, add a little bit of cornflour mixed with water at the end.