1 1/2 pounds medium boiling potatoes (about 3 medium potatoes)
2 teaspoons salt, divided, plus more to taste
1 1/2–2 pounds kale (15–20 large leaves), de-stemmed
1 cup chopped leeks or scallions
1 cup half-and-half or milk
1/2 teaspoon freshly ground black pepper
1/2 cup butter, melted
Put the whole potatoes in a large pot, cover with water, and bring to boil. Add 1 teaspoon of the salt and boil until the potatoes are tender, 15 to 20 minutes. Drain the potatoes and mash. Put in a heatproof dish and keep warm in a 200° oven.
Meanwhile, put the kale in a pot, cover with water, and bring to boil. Add the remaining 1 teaspoon salt and cook until the kale is tender, 15 to 20 minutes. Drain and finely chop the kale.
Place the leeks or scallions in a small pot, cover with the half-and-half, and cook over low heat until very soft, 15 to 20 minutes.
Add the kale to the warm potatoes and mix well. Add the half-and-half with leeks or scallions. Add the pepper; season with salt to taste. Spoon a little of the melted butter over each serving and serve hot.