Place the turnips in a saucepan with water to cover and 1 teaspoon of salt. Bring to a boil and simmer, covered, until easily pierced by a paring knife, about 35 minutes. Drain and return to the pot.

Meanwhile, in a small mixing bowl, combine the butter, miso, and half the scallions. Microwave until melted, about 10 seconds. Whisk until smooth.

Add half the miso butter to the turnips. Mash with a fork or potato masher until a coarse puree. Taste for seasoning.

Serve the turnips in a bowl with the remaining miso butter on top and garnish with the scallions.