Truffle Leek & Potato Soup

Soups, stews
3 tablespoons unsalted butter
4-5 medium leeks, cleaned, dark green sections removed, chopped
Heavy pinch of Kosher salt, plus more for seasoning
3 small Yukon Gold potatoes, peeled, diced
1 quart vegetable broth
1 cup heavy cream
1 cup buttermilk
1 tablespoon white truffle oil
1/2 teaspoon white pepper
1 tablespoon snipped chives
In a 6-quart saucepan over medium heat, melt butter. Add leeks and salt; sweat for 5 minutes. Decrease heat to medium-low and cook until leeks are tender, approximately 25 minutes, stirring occasionally. Add potatoes and vegetable broth, increase heat to medium-high and bring to a boil. Reduce heat to low, cover and gently simmer until potatoes are soft, approximately 45 minutes. Turn off heat, puree with an immersion blender until smooth. Stir in heavy cream, buttermilk, truffle oil and white pepper. Taste and adjust seasoning if desired. Sprinkle with chives and serve immediately, or chill and serve cold.