Bring the water and salt to a boil. Cook the broccoli until it’s crisp-tender and still a bright green in color. Drain, and refresh very briefly with cold running water. (Note: you can skip this step if you’re not in a hurry and have time to cool the broccoli.).
In the meantime, mix together all the remaining ingredients except the wasabi in a small pan, and stir over a low heat until the sugar is melted.
Let cool, and add the wasabi, reserving 1/2 tsp or so. Mix well until the wasabi is dissolved.
Pour the sauce over the broccoli and mix well.
Serve at room temperature or chilled, optionally with a little additional wasabi on the side for people to mix into the broccoli as they eat it (if they really like wasabi).