2 lbs. small thin-skinned potatoes
1 tsp. salt - divided
3 tbsp. finely chopped shallots or onions
1/2 tbsp. Dijon mustard
1 tbsp. whole-grain mustard
1 tbsp. white-wine vinegar, or to taste
1/2 tsp. black pepper
3 tbsp. olive oil
2 tbsp. chopped fresh flat-leaf parsley
Preheat oven to 400 degrees. Wash and dry potatoes. Place whole potatoes on a baking sheet and sprinkle with 1/2 tsp. salt. Roast potatoes until fork-tender. While potatoes are roasting, whisk together shallots, both mustards, vinegar, pepper, and remaining 1/2 tsp. salt in a large bowl, then add olive oil in a slow stream, while whisking until emulsified. While still warm, cut potatoes in half and add to vinaigrette. Sprinkle with chopped parsley and toss lightly to coat potatoes evenly with dressing. Serve warm or at room temperature.
