Cream the butter, peanut butter, granulated sugar, brown sugar, vanilla and egg.
In a separate bowl, combine the flour, baking powder and salt and combine with wet ingredients. Mix in the Reese's peanut butter chips.
Cover and refrigerate for 3 hours or up to overnight.
Preheat oven to 375 degrees.
Roll dough into 1 ½" balls, roll in granulated sugar and place 2 inches apart on a cookie sheet. Smash each cookie lightly with a fork and sprinkle with sea salt.
Bake for 9 minutes, remove from oven and transfer to a rack to cool.