Make a sugar syrup with sugar and water. You’ll know it is ready when you put a little ball of it in a cup of water and it drops to the bottom. Add butter and rum and mashed chestnut. Mix everything until it is cold. After that extend it until it is 1 cm.
Beat butter and confectioner’s sugar. Add chocolate and vanilla.
Put this stuffing on the dough and roll it. Sprinkle on top with powdered chocolate.