Hi Debra–please see my reply to Anne. But thanks to both because I’ll edit the recipe to include the description and a link if you can’t find it in your store.

Hi Anne–Mirin is sweet sake. You can find it in the Asian section of your supermarket. Kikkoman is one brand and the label is orange & yellow. You can also get it at Amazon http://amzn.to/2tnQMkj
You could substitute a medium white wine if you can’t find it, but I strongly advise using the Mirin because it does impart a wonderful flavor.