from bonappetit.com, serves 8-10
- 3 1/2 pounds fingerling potatoes, unpeeled, cut into 3/4'-1' pieces
- 1 tablespoon kosher salt plus more for seasoning
- 9 tablespoons (or more) extra-virgin olive oil, divided
- 2 tablespoons brown mustard seeds
- 3 medium leeks (white and pale green parts only), halved lengthwise, cut crosswise into 1/4' slices (about 5 cups)
- 1 tablespoon (or more) white wine vinegar
- 1 tablespoon Dijon mustard
- Freshly ground black pepper
1. Place potatoes in a large pot. Add enough cold water to cover by 3". Stir in 1 tablespoon salt and bring to a boil. Reduce heat to medium and simmer until potatoes are tender, about 10 minutes. Drain. Transfer to a large rimmed baking sheet and let cool slightly.
2. Heat 3 tablespoons oil in a small skillet over medium-high heat. Add mustard seeds to skillet and cook, stirring occasionally, until seeds start to pop, about 2 minutes. Pour oil with seeds into a large bowl.
3. Heat 2 tablespoons oil in a large skillet over medium heat. Add leeks, season with salt, and cook, stirring occasionally, until just tender, 10-12 minutes.
4. Wisk 4 tablespoons oil, vinegar, Dijon mustard, and 1 tablespoon water into mustard-seed oil. Add potatoes and leeks; toss to coat. Season with salt and pepper.