Preheat your oven to 400 degrees Fahrenheit. On a large rimmed baking sheet, toss the halved potatoes with the olive oil, salt, and pepper until they are well coated. Spread them out in a single layer, ensuring the cut sides are facing down to get that perfect golden crust. Roast for 20 to 25 minutes until the potatoes are just starting to become tender and slightly browned.
While the potatoes are in the oven, whisk together the Dijon mustard, whole grain mustard, heavy cream, minced garlic, dried thyme, and smoked paprika in a small bowl. The mixture should be thick, creamy, and fragrant.
Carefully remove the baking sheet from the oven. Pour the mustard cream mixture over the hot potatoes. Use a spatula or large spoon to toss the potatoes directly on the pan until every piece is generously coated in the sauce. Spread them back out into an even layer, though they can overlap slightly at this stage for a more rustic look.
Return the pan to the oven and bake for an additional 15 to 20 minutes. You are looking for the sauce to thicken and bubble, and the edges of the potatoes to become crispy and dark gold.
Remove the potatoes from the oven and let them sit for two or three minutes. This allows the sauce to set slightly and adhere better to the potatoes. Sprinkle with fresh chopped parsley and perhaps an extra pinch of cracked black pepper before transferring to a festive serving bowl.
