Serve this gingery hoisin dressing over hot or room-temperature steamed asparagus or as a dipping sauce for dumplings.
Grate ginger on the smallest holes of a box grater. To extract the juice, press the grated ginger in a fine sieve set over a small bowl or squeeze it in a piece of cheesecloth. (You should have about 1 tablespoon ginger juice.) Discard the pulp. Stir vinegar, hoisin sauce and scallions into the ginger juice.
Make Ahead Tip: Cover and refrigerate for up to 3 days.