Begin by preheating the oven to 350°F. Then, generously grease both the bottom and sides of an 8-inch springform pan, and finish by dusting it with powdered sugar.
In a 2-quart saucepan, blend chocolate chips and butter over low heat for 4-6 minutes until you achieve a smooth mixture. Afterward, incorporate nuts, sugar, and eggs before pouring the resulting mixture into your prepared pan.
Bake for 28-32 minutes, or until the edges gently detach from the sides of the pan. Allow it to cool completely before removing the springform pan sides and placing the cake on a serving plate.
In a saucepan, combine baking chocolate and whipping cream. Stir over low heat for 3-4 minutes until it's smooth. After cooling for 5 minutes, pour this mixture over the top and sides of your cooled cake. Refrigerate for a minimum of 1 hour for it to set.
For added indulgence, consider drizzling with melted chocolate and sprinkling with hazelnuts if desired.