1. In a medium heatproof bowl, microwave vinegar and sugar until warm but not hot, about 30 seconds. Stir to dissolve sugar, then add shallot and let cool to room temperature, about 10 minutes.
2. Meanwhile, cut cucumbers into 1/4"-thick slices and place in a large bowl. Once vinegar mixture has cooled, use a fork to transfer shallot rings to bowl with cucumbers and set aside. Whisk mustard, soy sauce, and miso into vinegar mixture, then gradually whisk in both oils until smooth.
3. Add herbs, sesame seeds, and dressing to bowl with cucumbers and toss gently to coat. Sprinkle with more herbs and sesame seeds before serving.
Source: Hannaford fresh Magazine, May-June 2021