Preheat oven to 375ºF.
In a small sauce pan, combine butter and cocoa powder.
On a work surface, lay the pie dough rounds out next to each other. Brush both rounds liberally with butter-cocoa powder mixture and sprinkle each round with 2 tablespoons of granulated sugar.
Top one of the rounds with all of the chopped hazelnuts.
Gently pick up the round without nuts, turn it over and place it on top of the round with nuts, chocolatey sides facing together.
Gently roll a rolling pin over the top of the pie dough so the two rounds seal together and the round is 13 inches in diameter. Cut into 16 equal wedges like a pie.