Preheat oven to 350°F (175°C).
Cream butter and powdered sugar, then add vanilla.
Mix in hazelnut flour and all-purpose flour to form dough.
Roll, cut, and bake dough for 10-12 mins.
Heat cream, pour over chocolate and butter, stir for ganache.
Sandwich cooled cookies with ganache.
Optional: dust with powdered sugar.
