Fingerling Potato Salad

Ingredients

• 10 servings pepper black freshly ground
• 2 tablespoons brown mustard seeds 
• 1 tablespoon dijon mustard 
• 3.5 pounds fingerling potatoes unpeeled cut into 3/4"-1" pieces
• 1 tablespoon kosher salt plus more for seasoning
• 5 cups leek white halved lengthwise ( and palegreen parts only)
• 9 tablespoons olive oil extra virgin extra-virgin divided ()
• 1 tablespoon citrus champagne vinegar ()

Equipment

• bowl
• frying pan
• baking sheet
• whisk
• pot

Directions

1. Place potatoes in a large pot.
2. Add enough cold water to cover by 3". Stir in 1 tablespoons salt and bring to a boil. Reduce heat to mediumand simmer until potatoes are tender, about 10 minutes.
3. Drain.
4. Transfer to a large rimmed baking sheet and let cool slightly.
5. Heat 3 tablespoons oil in a small skillet over medium-high heat.
6. Add mustard seeds to skillet and cook, stirring occasionally, until seeds start to pop, about 2 minutes.
7. Pour oil with seeds into a large bowl.
8. Heat 2 tablespoons oil in a large skillet over medium heat.
9. Add leeks, season with salt, and cook, stirring occasionally, until justtender, 10-12 minutes.
10. Whisk remaining 4 tablespoons oil, vinegar, Dijon mustard, and 1 tablespoon water into mustard-seed oil.
11. Add potatoes and leeks; toss to coat. Season with salt and pepper. DO AHEAD: Can be made 1 day ahead. Cover; chill. Return to room temperature before serving, adding more oil and vinegar if dry.