I made this recipe and, as I recall, the miso is for the mashed potatoes. You can make the mashed potatoes the way that you normally would and I'm sure it would be fine.
One thing that I did learn in this recipe is that when it calls for 1/2 cup of water or broth, it means 1/2 cup. I sometimes find I need a little more water/broth when cooking vegetables. In this recipe I used a cup of broth and it came out very runny and even made my mashed potatoes runny, as well.

Also, my husband and I are fans of spices. We found the recipe by itself to be too bland. Don't hesitate to add whatever you would normally use in the way of spices.
Good luck.
