Wipe off any dirt on oyster mushrooms and split them into bite size pieces. Set aside
Mince garlic and ginger. Chop Thai chili.
Bring a pot of water to boil. Blanch oyster mushrooms for 1-2 minutes. Immediately remove and soak in cold water to stop cooking.
In a bowl, combine minced garlic, ginger, chili powder, soy sauce, black vinegar and sugar to make a sauce. Heat up 3 tbsp of cooking oil, pour over the sauce and mix well.
Pour sauce onto blanched oyster mushrooms and add in Thai chili. Mix well.
Garnish with green onion and sesame seeds before serving.