Murasaki sweet potatoes with miso scallion butter

8 pieces Murasaki sweet potatoes
small in size, about 4-5 pounds total
1 1/2 sticks unsalted butter
2 tbsp white miso paste
3 tbsp scallion
finely chopped
Let's face it ... in this recipe, the murasaki sweet potato is simply a vessel for the miso butter! ;) This super simple recipe is a crowd-pleaser. We often whip it up when entertaining guests.
Soften the butter a few hours ahead of time.
Preheat oven to 450°F with rack in the upper third.
Wash the potatoes then prick them all over with a fork and put on a foil-lined large baking sheet. Bake until very soft when squeezed, 45 minutes to 1 hour.
While potatoes bake, stir together butter, miso, and scallion until combined.
Slit hot potatoes lengthwise and, using oven mitts, push in the sides to puff up and scrunch the potato. Serve with some scallion butter in center of each and with additional scallion butter on the side.
source: Epicurious but originally from Gourmet November 2007
We often roast extra sweet potatoes for our one-year-old daughter. When they cool, the potatoes shrink away from the skin and become really easy to peel. We cube them at that point and freeze any extras.

The miso-scallion butter can be made 4 days ahead and chilled, covered. Soften at room temperature and stir before using. The sweet potatoes can be roasted (but not cut) 4 hours ahead and kept at room temperature, covered with foil. Reheat potatoes on a baking sheet on middle rack of a 350°F oven until heated through, about 20 minutes.