- 1/4 cup Champagne vinegar
- 2 tablespoons mustard seeds
- 6 tablespoons Dijon mustard
- 1 tablespoon coriander seeds, crushed
- Coarse kosher salt
- 3 pounds russet potatoes, peeled, cut into 1 1/2- to 2-inch cubes
- 6 tablespoons vegetable oil
- Preheat oven to 425°F. Bring vinegar and mustard seeds to boil in small saucepan. Reduce heat; simmer until almost dry, stirring occasionally, about 5 minutes. Transfer to large bowl. Add Dijon mustard and coriander. Season with coarse salt and pepper. Place potatoes in large saucepan; add water to cover by 1 inch; sprinkle with coarse salt. Boil 3 minutes. Drain; return to pan. Cook over medium-high heat until dry, shaking pan occasionally, 3 minutes.
- Meanwhile, drizzle 6 tablespoons oil over large rimmed baking sheet. Place sheet in oven 10 minutes to heat.
- Add potatoes to mustard mixture; toss. Spread potatoes on hot baking sheet (oil may splatter). Sprinkle with coarse salt and pepper. Roast 15 minutes. Turn potatoes; roast until browned and tender, about 15 minutes longer. Season with coarse salt and pepper and serve hot.