Preheat oven to 350° F. Butter 10-inch springform pan, then line bottom with parchment paper. In a heavy sauce pan over low heat, melt butter with chocolate chips until melted and smooth. Whisk in sugar and cocoa powder until smooth. Add eggs and whisk until mixture is combined well and smooth. Pour batter into prepared pan.
Bake for 45 minutes until toothpick inserted in center comes out clean. Allow to cool completely on a wire rack. Run a knife around egde of pan then release pan sides.
Optional Toppings
For Powdered Sugar with Fresh Raspberries, using a fine mesh strainer dust top with powdered sugar and decorate with raspberries and raspberry puree.
For Caramel and Ice Cream, it's best to scoop ice cream balls several hours in advance and refreeze them so they hold their shape. Drizzle cake with caramel sauce and top with ice cream balls.