Prepare the Roasted Garlic Confit: Preheat the oven to 300°F (150°C). Slice the tops off the garlic heads to expose the cloves. Place them in a small baking dish, cut side up. Pour olive oil over the garlic, ensuring they are well submerged. Add thyme, rosemary, and a pinch of salt. Cover the dish with aluminum foil and roast for about 45 minutes, or until the cloves are soft and golden brown. Remove from the oven and let cool. Squeeze the roasted garlic cloves out of their skins and set aside.

Prepare the Smoked Leek Compound Butter: In a skillet over medium heat, add sliced leeks and sauté until they are soft and slightly caramelized, about 10 minutes. Allow to cool. In a mixing bowl, combine softened butter, smoked paprika, lemon juice, sautéed leeks, salt, and pepper. Mix until well combined. Place the butter mixture on a piece of parchment paper, shape it into a log, and refrigerate until firm.

Prepare the Prime Rib: Preheat the oven to 450°F (230°C). In a small bowl, mix chopped rosemary, thyme, salt, pepper, and garlic powder. Rub the prime rib with olive oil, then coat it evenly with the herb mixture. Place the roast in a roasting pan, bone side down, and roast for 20 minutes. Reduce the oven temperature to 325°F (160°C) and continue roasting until the internal temperature reaches your desired doneness (about 130°F for medium-rare), approximately 1.5 to 2 hours. Remove the prime rib from the oven and let it rest for at least 20 minutes before slicing.

Serve: Slice the prime rib and serve it with a drizzle of roasted garlic confit and slices of smoked leek compound butter.