1 1/2 pounds Yukon Gold potatoes, peeled and cut into 1/4 -inch dice
2 small leeks, white part only, cut into 1/4 -inch dice
2/3 cup crème fraîche
1 tablespoon sherry vinegar
2 tablespoons minced chives
Salt and freshly ground white pepper
Bring a large saucepan of salted water to a boil. Add the potatoes and cook until barely tender, about 2 minutes. Add the leeks and cook until the potatoes are tender, about 2 to 3 minutes longer. Drain the potatoes and leeks and cool under running water. Drain again and pat thoroughly dry with paper towels.
In a medium bowl, whisk the crème fraîche with the sherry vinegar and chives and season with salt and white pepper. Fold in the potatoes and leeks and serve.
The potato salad can be refrigerated for up to 1 day. Bring to room temperature before serving.