Author Notes: In my take on potato salad, mini spuds are roasted at high heat, then tossed in a pleasantly bracing mustard and walnut oil vinaigrette. Filled with plenty of toasted walnuts, fresh basil, and sliced scallions, this potato salad is best eaten at room temperature. I recommend gently smashing some of the potatoes to break their skins—this allows the vinaigrette to better penetrate the starchy goodness.

Roasted Potato Salad With Mustard-Walnut Vinaigrette

Serves: 6 to 8 
Prep time: 45 min 
Cook time: 45 min

Ingredients

For the salad

• 4pounds mixed marble potatoes, or other small potatoes
• 1cup walnuts, toasted and roughly chopped
• 1bunch basil, leaves torn into bite-sized pieces
• 1bunch scallions, white and green parts thinly sliced crosswise

For the vinaigrette

• 2cloves garlic, peeled
• 1tablespoon whole-grain mustard
• 1tablespoon Dijon mustard
• 2tablespoons lemon juice
• 1tablespoon red wine vinegar
• 2tablespoons roasted walnut oil
• 1/4cup extra-virgin olive oil
• 1pinch sea salt and freshly ground black pepper, to taste

Directions

1. Preheat oven to 425° F and line two rimmed baking sheets with parchment paper.
2. Wash and dry potatoes, then spread evenly between baking sheets. Drizzle with olive oil and toss to evenly coat potatoes. Sprinkle with freshly-ground black pepper and sea salt, then roast, shaking the pans occasionally, until potatoes are tender and browning (about 45 minutes, depending on the size of your potatoes).
3. Meanwhile, prepare vinaigrette. Place garlic cloves on a cutting board, sprinkle with a generous couple pinches of sea salt, and chop and mash with the side of your knife until the clove breaks down into a salty paste.
4. Add garlic paste to a small bowl along with mustards, lemon juice, and vinegar. Whisk to emulsify. Add olive and walnut oils and whisk vigorously to combine. Taste and adjust seasoning with additional sea salt and pepper.
5. When potatoes are done, transfer to a large bowl. Add scallions and dressing, and toss to coat. Using the back of a mixing spoon or the end of a wooden spatula, roughly smash some of the potatoes to break the skins. You’re not making mashed potatoes, but breaking the potatoes down will allow them to soak up more of the vinaigrette.
6. Allow dressed potatoes to sit at room temperature for about 45 minutes to one hour. Just before serving, stir in walnuts and basil.

https://food52.com/recipes/28744-roasted-potato-salad-with-mustard-walnut-vinaigrette