1 1/2 cup shiitake mushrooms (stems removed and sliced into bite size strips)
1 2/3 cup dashi stock or vegetable broth
1/2 teaspoon granulated sugar
2 tablespoon soy sauce
1 tablespoon mirin
1/2 teaspoon kosher salt
1 tablespoon cornstarch mixed with 1cold water
Bring a pot of water to boil and the potatoes. Boil until tender (about 10 minutes), drain and put them back in the pot. Add milk and mash until the potatoes are smooth. Season with salt and pepper and set aside.
In a large pan over high heat, add dashi, sugar, salt, mirin and light soy. Bring to a boil and add mushrooms. Lower heat to a simmering boil and cook for about 10 minutes, until mushrooms are soft.
Add cornstarch and water mixture and stir well.
Serve the easy mashed potatoes in a large bowl topped with mushrooms sauce and scallions or divide into 4-6 equal servings.