Soak the Black Beans: Place fermented black beans in a bowl of cold water and soak for 1 hour. Drain, rinse well, and lightly mash most of the beans, leaving a few whole for texture.
Heat the Oils: Heat sesame oil and neutral oil together in a small saucepan over medium heat.
Cook Aromatics: Add minced garlic, ginger, and prepared black beans. Sauté for about 1 minute until fragrant, stirring constantly to prevent burning.
Add Seasonings: Stir in Shaoxing wine, dark soy sauce, rice vinegar, sugar, and black pepper. Mix well to combine flavors.
Simmer the Sauce: Pour in the stock and bring the mixture to a gentle boil. Reduce heat and let it simmer for 4–5 minutes.
Thicken the Sauce: In a small bowl, mix cornflour with cold water to form a slurry. Slowly add it to the sauce while stirring until thick and glossy.
Taste & Adjust: Taste the sauce and adjust salt, sugar, or vinegar if needed. Remove from heat and let cool slightly before use.
