Flourless Chocolate Hazelnut Torte

Position rack in center of oven and preheat to 350°F. Butter 9-inch-diameter springform pan. Line bottom of pan with parchment paper round. Wrap outside of pan tightly with 3 layers of heavy-duty foil. Combine chocolate and butter in a microwave-safe bowl. Microwave for 45 seconds and stir. Repeat. Microwave for 20 second intervals, stirring after each one, until smooth. Watch carefully to avoid burning (or reduce the microwave's power if it's particularly aggressive). Set aside and cool slightly.

Whisk eggs, brown sugar, and 1/4 cup Frangelico in large bowl to blend. Add chocolate mixture and whisk until smooth. Stir in ground hazelnuts and 1 teaspoon coarse kosher salt. Transfer batter to prepared pan. Place springform pan in large roasting pan and place in the preheated oven. Pour enough hot water into roasting pan to come halfway up sides of springform pan. Tent springform pan loosely with foil. Bake until cake is set in center and top is not quite dry to the touch, about 1 1/2 hours (top of cake will remain shiny and sides will have pulled away from the springform pan; a cake tester won't come out clean–it will have moist crumbs). Remove cake from roasting pan; remove foil from top and and place on a rack. When cool enough to handle, remove foil from outside of pan and cool completely. Cover with foil and refrigerate cake at least 3 hours, preferably overnight. You can make the cake up to 3 days ahead.

Using electric mixer, beat whipping cream and remaining 1/4 cup Frangelico in medium bowl until soft peaks form. Release pan sides. Keep the cake on the pan base and transfer to a larger platter if you want to bring the whole cake to the table. Cut cake into wedges. Transfer to plates. Top with whipped cream; sprinkle with chopped toasted hazelnuts. Serve cake chilled, directly from refrigerator.