- One 10-pound, bone-in prime rib roast (about 4 bones), tied
- Sea salt
- Freshly ground pepper
- 1/4 cup extra-virgin olive oil
- 4 tablespoons unsalted butter
- 2 heads of garlic, halved crosswise
- 8 thyme sprigs
- 2 cups crème fraîche (16 ounces)
- 1/2 cup grated peeled fresh horseradish
- 1 tablespoon Champagne vinegar
- 1 tablespoon minced chives
- 1 tablespoon minced scallion
- 1 teaspoon salt
- 1 teaspoon cracked black pepper
- 1/4 teaspoon piment d'Espelette or cayenne pepper (see Note)
- Prepare the roast Preheat the oven to 325°. Using a sharp paring knife, make 1-inch-deep slits all over the surface of the meat. Rub salt and pepper all over the outside and in the slits of the roast. Heat the olive oil in a very large skillet. Add the roast, meaty side down, and cook over high heat until browned, about 10 minutes. Add the butter, garlic and thyme and cook over moderate heat, basting the roast with the butter, for 5 minutes.
- Prepare the roast Transfer the roast to a medium roasting pan, bone side down. Press the cut side of the garlic halves and the thyme sprigs onto the surface of the meat and roast, turning the pan occasionally, for about 3 1/2 hours; the meat is done when an instant-read thermometer inserted in the center registers 125°. Let rest for 15 minutes.
- Meanwhile, make the sauce Combine all of the ingredients in a bowl.
- Meanwhile, make the sauce Carve the roast off the bone, then thinly slice. Serve with the horseradish sauce.
Piment d'Espelette, a Basque red chile powder, is available at specialty food stores and online at vannsspices.com.
Rich, slow-cooked meats call for a substantial red wine with a tannic backbone, like Barolo.