In a small bowl, combine the softened butter, chopped tarragon, cognac, and roasted garlic paste. Mix well until all ingredients are fully incorporated.

Place the mixture onto a piece of plastic wrap and shape it into a log. Wrap tightly and refrigerate until firm, about 30 minutes.

Preheat your oven to 400°F (200°C). Season the porterhouse steak generously with salt and freshly cracked black pepper on both sides.

In a large oven-safe skillet, heat the olive oil over medium-high heat. Once hot, add the seasoned porterhouse steak and sear for about 4-5 minutes on one side until a nice crust forms. Flip the steak over.

Immediately place the thinly sliced prosciutto over the top of the steak, covering it completely. Drizzle the black truffle oil over the prosciutto.

Transfer the skillet to the preheated oven. Roast the steak for about 10-15 minutes for medium-rare, or until it reaches your desired doneness. Use a meat thermometer for accuracy; aim for 130°F (54°C) for medium-rare.

Once the steak is cooked, remove it from the oven and let it rest for 5-10 minutes. This allows the juices to redistribute.

Slice the porterhouse steak and serve with a generous dollop of the tarragon and cognac confit butter on top. Garnish with fresh tarragon leaves for an added touch.