Using a mandolin or sharp knife, thinly slice the cucumber and add into a medium bowl.
In a small bowl, whisk all of the dressing ingredients together. Pour the dressing over the cucumbers and toss together.
Add sliced green onions and sesame seeds, then lightly toss together one last time.
Let the salad marinate in the dressing for 5 minutes, then serve.
The cucumbers only need to marinate for 5 minutes in the Asian dressing before serving. You can let them sit for longer, however, the cucumbers will naturally release their liquid the longer they sit. This will thin out the dressing slightly.
Leftovers can be stored in an airtight container in the fridge for up to 3 days. Any longer and the cucumber slices may lose their crunch and the dressing will become watery.