Butter:
1/4 cup (1/2 stick) unsalted butter, softened
1 ounce prosciutto, very finely chopped
1 medium shallot, minced
1 tablespoon finely chopped fresh basil leaves
1 tablespoon freshly grated Parmigiano-Reggiano® Cheese
1/4 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
Chicken:
8 chicken thighs, bone-in, skin-on, each 5 to 6 ounces, trimmed of excess fat and skin
1/2 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
In a small bowl combine all the butter ingredients and mix together with a fork. Divide the butter into eight equal portions.
Prepare the grill for direct and indirect cooking over medium-high heat (400° to 500°F).
Pat the chicken thighs dry with paper towels. Using your fingertips, gently loosen the skin on the thighs, being careful not to separate the skin completely from the meat. Lift the skin up and place a portion of the butter underneath. Smooth the skin over the butter and massage gently to spread the butter evenly over the meat. Season the thighs on both sides with the salt and pepper.
Brush the cooking grates clean. Grill the thighs, skin side up first, over indirect medium-high heat, with the lid closed, until sizzling, slightly firm, and lightly marked on the underside, 18 to 20 minutes. Turn the thighs over, move to direct medium-high heat, and cook, with the lid closed, until the juices run clear, the skin is blistered and crisp, and the meat is no longer pink at the bone, 2 to 4 minutes more (if flare-ups occur, move the thighs temporarily over indirect heat). Remove the thighs from the grill, let rest for 3 to 5 minutes, and then serve warm.