Simmered potato with dashi and butter

Ingredients (for 4 people)

4 potato (May Queen potato variety) I recommend
800cc dashi
100cc light soy sauce
100cc mirin
pinch of salt
20g butter
choppped green onion

*dashi
  http://japanesehomecooking-okaasan.blogspot.jp/2011/06/how-to-make-dashijapanese-soup-stock.html

Process

1. Peel potato.
2. Pour dashi, and potato into a deep pan. And cook the low heat.

3. Add soy sauce and mirin and continuously cook the low heat for 1hour.
4. Add butter into 3process and cook the low heat for 10minutes. Please pay attention not to melt potato.
5. Serve potato and soup and garnish with chopped green onion.