Place the Chinese black beans in a small bowl, cover with warm water, and soak for 5 minutes.
Drain and set aside.
Heat the oil in a skillet or small saucepan over medium heat.
Add the minced ginger, garlic, and sliced green onion, and sauté for 1 minute until fragrant.
Add the soaked black beans, vegetarian dashi, rice vinegar, soy sauce, and salt.
Bring the mixture to a rolling boil.
Whisk in the dissolved potato starch mixture.
Reduce the heat and simmer, stirring constantly, for 2 minutes or until the sauce has thickened to your desired consistency.
Use immediately or transfer to an airtight container and refrigerate for later use.
