* 4 lbs large Yukon gold potatoes, unpeeled and scrubbed (or Russets, peeled)
* Salt and freshly ground pepper
* 1/2 cup unsalted butter
* 4 leeks, including tender green parts, finely chopped and well rinsed
* 1 cup sour cream at room temperature
* 1 cup milk, heated to a simmer
Cut the potatoes into large, uniform chunks. Put the potato chunks in a large saucepan and add water to cover and a generous pinch of salt. Bring to a boil over medium heat, cover partially, and cook the potatoes, stirring once or twice, until the potatoes are very tender, about 40 minutes. Drain.
Meanwhile, in a frying pan over medium heat, melt the butter. Add the leeks, cover and cook, stirring once or twice, until tender and lightly browned, 12-15 minutes. Set aside and keep warm.
Return the potatoes to the saucepan and place the pan over low heat. With a potato masher, mash the potatoes thoroughly. Stir in the leeks and their buttery juices. Add the sour cream and stir well. Add the hot milk, 1/2 teaspoon salt, and 1 teaspoon pepper and stir vigorously until light and fluffy.
Remove the pan from the heat. Taste and adjust the seasoning with salt and pepper. Serve hot.
Taken from Thad’s Recipe Collection, which was in turn taken from the Williams-Sonoma Thanksgiving Cookbook.