Preheat the oven to 450°F (230°C).

In a dry skillet over medium heat, toast the fenugreek seeds and black peppercorns until fragrant, about 3-5 minutes. Remove from heat and let cool slightly.

In a spice grinder or mortar and pestle, coarsely grind the toasted fenugreek and black peppercorns. Combine with kosher salt in a small bowl.

Rub the prime rib roast all over with olive oil, then evenly coat it with the fenugreek and peppercorn mixture, pressing it into the meat.

In a separate bowl, mix the mashed black garlic, softened butter, fresh thyme, and rosemary until well combined.

Place the seasoned prime rib in a roasting pan, bone-side down. Spread the black garlic and herb butter evenly over the top of the roast.

Roast the prime rib in the preheated oven for 20 minutes to create a crust. Reduce the temperature to 325°F (160°C) and continue roasting for about 1.5 to 2 hours, or until the internal temperature reaches 130°F (54°C) for medium-rare.

Remove the roast from the oven and tent it with foil. Let it rest for 20-30 minutes before slicing.

Drizzle with Worcestershire sauce before serving and garnish with fresh thyme sprigs.