Remove the Porterhouse steaks from the refrigerator and let them rest at room temperature for about 30 minutes. Preheat your grill or cast-iron skillet over medium-high heat.

In a small bowl, combine the smoked sea salt and chopped rosemary. Rub the steaks with olive oil, then generously coat both sides with the smoked sea salt and rosemary mixture. Ensure an even coating.

Place the seasoned Porterhouse steaks on the grill or skillet. Cook for about 4-5 minutes on each side for medium-rare, adjusting the time based on your preferred doneness. Once cooked, remove the steaks and let them rest for about 10 minutes to allow the juices to redistribute.

In a saucepan over medium heat, add the chopped shallots. Sauté until translucent, about 3-4 minutes. Add the red currants and cook for another 2-3 minutes until they start to break down.

Pour in the beef stock and balsamic vinegar, bringing the mixture to a simmer. Let it simmer for about 10 minutes, reducing slightly. Stir in the unsalted butter until melted and the sauce is glossy. Season with freshly cracked black pepper to taste.

Slice the rested Porterhouse steaks and place them on serving plates. Drizzle the red currant and shallot jus over the steaks or serve on the side. Garnish with additional fresh rosemary if desired.