In a small saucepan over low heat, combine the black garlic and minced shallots with 1 tablespoon of butter. Cook gently for about 10 minutes until the shallots are soft and translucent.

Remove from heat and let cool slightly. In a bowl, combine the black garlic mixture with the remaining softened butter, lemon juice, and parsley. Mix until well combined. Set aside.

Preheat your oven to 400°F (200°C).

Pat the ribeye steaks dry with paper towels. Rub both sides with olive oil and season generously with salt and pepper.

Heat a large oven-safe skillet over medium-high heat. Once hot, add the ribeye steaks and sear for 4-5 minutes on each side until browned.

After searing, scatter the sliced leeks and chopped rosemary around the steaks in the skillet.

Transfer the skillet to the preheated oven. Roast the steaks for about 10-15 minutes, or until they reach your desired level of doneness (130°F for medium-rare).

Remove the skillet from the oven and let the steaks rest for 5-10 minutes. This allows the juices to redistribute.

Top each steak with a generous dollop of the black garlic and shallot confit butter. Garnish with additional parsley if desired. Serve with the roasted leeks.