In bowl, combine the flour, sugar, cocoa powder, baking powder and salt. Add butter, eggs and vanilla. Stir until well combined, will be thick.
Cover, refrigerate for 1/2 an hour, until firm. Heat oven to 325. Line baking sheets w/ parchment paper. Place coarse sugar in a shallow bowl.
Roll heaping tbsps of dough into balls, then roll in coarse sugar. Place dough balls 1" apart on baking sheets. Lightly flatten each dough ball, and make a deep indentation in the center w/ your thumb. Bake 10 mins. Remove from oven. In small bowl, whisk together peanut butter and powdered sugar. Place chocoalte chips in microwaveable bowl, microwave until melted. Fill 1/2 the cookies w/ peanut butter mix, and the other 1/2 w/ the melted chocolate. Refrigerate until set, about 1/2 an hour.