In a small bowl, combine the softened Kerrygold butter, fresh chives, minced garlic, kosher salt, black pepper, and smoked paprika. Mix until well incorporated and the herbs are evenly distributed throughout the butter. Shape the mixture into a log about 1 inch in diameter on a piece of parchment paper, then roll it tightly and refrigerate for at least 1 hour until firm enough to slice. I find that rolling it in parchment makes it much easier to handle and slice cleanly later.

While the butter chills, scrub the large Russet potatoes under cold water to remove any dirt, then pat them dry completely. Place each potato on a cutting board and position wooden spoons or chopsticks on either side of it—these will act as guides to prevent your knife from cutting all the way through the bottom. This setup is crucial for hasselback potatoes, as you want thin slices that remain attached at the base.

Using a sharp knife, make thin, parallel cuts across each potato perpendicular to the board, spacing them about 1/4 inch apart. The wooden spoons will stop your blade before it cuts through the bottom, keeping the potato intact. Once all potatoes are sliced, remove the chilled herb butter from the refrigerator and slice it into thin pats. Carefully insert butter slices into each cut in the potatoes, distributing them as evenly as possible throughout. I like to work quickly here so the butter doesn't warm up too much and slide around inside the slits.

Place each stuffed potato on a large sheet of heavy-duty aluminum foil. Drizzle the top of each potato lightly with extra-virgin olive oil and season generously with coarse sea salt. Fold the foil up and around each potato to create a sealed packet, leaving a little space at the top for steam to circulate. This foil wrapper is essential—it traps the heat and moisture, allowing the potatoes to steam from the inside while the exterior can develop some color.

Preheat your grill to medium-high heat (around 375-400°F) and establish a cool zone by having heat on only one side. Place the foil-wrapped potatoes on the cooler side of the grill, away from direct flames. Close the grill lid and cook for 45 to 50 minutes, until the potatoes are completely tender when pierced with a fork through the foil. Check occasionally to ensure even cooking, rotating the packets if needed for uniform heat distribution.

Carefully remove the potatoes from the grill using tongs or heat-resistant gloves, as the foil will be extremely hot. Gently unwrap the foil (watch out for the steam!) and transfer each potato to a serving plate. The butter will have melted into the slices, creating a creamy, herb-infused interior. Serve immediately while hot, optionally adding any extra melted butter from the packet and a final sprinkle of coarse sea salt to taste.