Preheat oven to 325 degrees F. Butter and parchment a 9-inch cake pan
In the bowl of a food processor, grind chocolate and hazelnuts down to a fine paste. Add soft butter and sugar and pulse until thoroughly incorporated. Add eggs 1 by 1. Scrape down bowl carefully. Add flour. Fill prepared cake pan with torte batter. Spread carefully to level and bake for 20 to 25 minutes until cake tester comes out clean.