Chop or break the couverture into chunks and melt over a hot water bath. Grind the sugar into powdered sugar in a coffee grinder. Lightly roast the sunflower seeds in a pan. Dust with the powdered sugar and caramelize. Transfer the caramelized sunflower seeds in into the melted chocolate and mix well. Pour everything onto the baking sheet and spread out evenly to about 0.5 - 1.0 cm thick. Let cool for 2 hour and break the chocolate into big chunks.