1 1/2 pounds russet potatoes (about 5 medium), peeled
2 cups finely chopped leeks (use white and pale-green portions), about 2 large leeks
1/4 cup chopped fresh basil leaves
2 tablespoons olive oil
About 1/4 to 1/3 cup butter, melted
About 1/3 to 1/2 cup cream or milk
Salt and freshly ground pepper, to taste
Cut the potatoes into quarters, then place them in a large saucepan with enough water to cover by about 1/2 inch. Bring water to a boil over high heat, reduce to low, cover and cook until potatoes are soft, about 25 to 35 minutes.
Meanwhile, saute the leeks and basil in the olive oil over medium-low heat until leeks are very soft, about 15 minutes. Add desired amount of butter to leek mixture and 1/3 cup of the cream or milk. Bring this mixture to a simmer then remove from heat; set aside.
When potatoes are tender, drain well then mash into a puree. Stir in leek-cream mixture, then adjust seasonings with salt and pepper, adding additional cream or milk to reach desired consistency.
To prepare ahead, spoon potato mixture into a lightly oiled baking dish. Refrigerate for up to 24 hours. About 35 minutes before serving, either dot potatoes with butter or margarine or brush with olive oil, then reheat in a preheated, 350-degree oven until hot, about 25 to 30 minutes.
Makes 6 servings.