Why This Recipe Works

We wanted a roasted potato side dish that was packed with complex mustard flavor. To achieve this, we started by coating the potatoes in bold Dijon mustard before roasting them, but unfortunately this resulted in a tacky and leathery potato once roasted. Instead, we found that the solution was to combine whole-grain mustard with olive oil to evenly coat the outsides of the potatoes. The oil added richness, which kept the potatoes from turning out leathery. And the mustard seeds roasted along with the potatoes, becoming nutty and crisp. The satisfying pop was a welcome contrast to the creamy, lightly browned potatoes. After roasting, we tossed the potatoes with Dijon mustard, more olive oil, garlic, and lemon zest and juice to boost the mustard flavor. Using two types of mustard ensured that the potatoes were boldly flavored. For herby flair, we added rosemary both before and after cooking. Cooking the rosemary allowed it to deepen in flavor, while adding it after cooking provided freshness to the dish.

Before You Begin

Use small red potatoes measuring 1½ to 2 inches in diameter.

Instructions

Adjust oven rack to lowest position and heat oven to 350 degrees. Line rimmed baking sheet with parchment paper. Toss potatoes, ¼ cup oil, whole-grain mustard, 1 tablespoon rosemary, ¾ teaspoon salt, and pepper in large bowl until potatoes are evenly coated with oil mixture. Arrange potatoes cut sides down on prepared sheet. Roast until potatoes are tender and bottoms are golden brown, 50 minutes to 1 hour.

Whisk Dijon mustard, garlic, lemon zest and juice, remaining 2 tablespoons oil, remaining 1 teaspoon rosemary, and remaining ¼ teaspoon salt in large bowl until smooth.

Transfer roasted potatoes to bowl with Dijon mixture and toss until potatoes are evenly coated. Season with salt and pepper to taste. Serve.