This sweet and sour sauce is the one I grew up with in Shanghai. It's made with black vinegar, rock sugar, and generally served atop tender pork riblets.
Ingredients
9 medium scallions
8 cloves garlic
1 (2-inch) piece fresh ginger
1/4 cup chopped fresh cilantro
2 tablespoons neutral oil, such as vegetable or canola
2 tablespoons Shaoxing wine
3/4 cup soy sauce
3/4 cup black vinegar
3 tablespoons granulated sugar, or 50 grams rock sugar
1/4 cup cold water
1 tablespoon cornstarch
2 teaspoons toasted sesame oil
Instructions
Trim and chop 9 medium scallions. Thinly slice 8 garlic cloves. Peel and thinly slice 1 (2-inch) piece fresh ginger. Coarsely chop until you have 1/4 cup chopped cilantro.
Heat 2 tablespoons neutral oil in a medium saucepan over medium heat until shimmering. Add the scallions, garlic, and ginger, and sauté until very fragrant, 2 to 3 minutes. Add 2 tablespoons Shaoxing wine and reduce for a few seconds. Add 3/4 cup soy sauce and 3/4 cup black vinegar, and bring the mixture to a light simmer.
Add 3 tablespoons granulated sugar or 50 grams rock sugar, stir until melted, and let simmer 15 minutes. Add the cilantro, remove from the heat, and let infuse for 5 minutes.
Pour the mixture through a fine-mesh strainer into a medium bowl, then discard the contents of the strainer. Pour the sauce back into the saucepan and bring to a boil over medium-high heat.
Meanwhile, stir 1/4 cup cold water and 1 tablespoon cornstarch together in a small bowl until the cornstarch is dissolved.
When the sauce is boiling, add the cornstarch slurry and whisk until the mixture thickens considerably. Remove from the heat and stir in 2 teaspoons toasted sesame oil.
