Preheat oven to 375ºF.
In a small saucepan, melt the 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 over and place it on top of the round with nuts, buttered sides facing together.