Grilled Chive Butter Flavored Potatoes

1 stick butter, softened1 c. finely chopped chives, divided½ c. sour cream, plus more for serving2 t. kosher salt2 t. black pepper4 (10-oz.) baking potatoes1. In bowl, combine butter, ¾ c. chives, ½ c. sour cream, salt and pepper. Mix…