Ingredients

• 3 tablespoons butter
• 4 large leeks (white and pale green parts only), quartered lengthwise, thinly sliced crosswise
• 1 1/2 pounds russet potatoes, peeled, cut into 1-inch pieces
• 2 1/4 cups water
• 1/4 cup sour cream

Instructions

1. Melt butter in heavy large saucepan over medium heat. Add leeks; sauté until just beginning to color, about 15 minutes. Add potatoes and water. Season with salt. Increase heat to high; bring to boil. Cover; boil until potatoes are tender, about 20 minutes. Uncover; boil until almost all liquid evaporates, about 5 minutes.
2. Mash potatoes coarsely; mix in sour cream. Season with salt and pepper. (Can be made 2 hours ahead. Cover; let stand at room temperature. Rewarm over low heat, stirring.) Transfer to large bowl.