Make the Cake

1. Preheat the oven to 325°F. Line the bottom of a 9-inch springform pan with parchment paper and grease the sides of the pan. Prepare the pan for a water bath (see how I like to prepare my water bath). Bring a kettle or pot of water to a boil.
2. Add the eggs to a large mixing bowl and use the whisk attachment to whip at high speed until the volume doubles, about 5 minutes.
3. While the eggs whip, melt the chocolate and butter together. You can melt them in a double boiler or in the microwave.
4. Fold the egg mixture into the chocolate in three roughly equal parts. So, add about a third of the egg mixture to the chocolate and fold together until mostly combined. Then add another third and fold it in, then the remaining third until fully combined.
5. Pour the batter into the prepared pan and spread evenly. Place the springform pan into a larger pan and fill the larger pan with boiling water that comes halfway up the sides of the springform pan.
6. Bake the cake until it has risen slightly, the edges are just beginning to set and a thin crust has formed on top, and an instant read thermometer inserted in the middle registers 140°F, about 18-20 minutes. It make look a little under baked, but it will continue to cook as it cools and firms up.
7. Remove the springform pan from the water bath and set on a wire rack to cool to room temperature (the center will still be soft), then refrigerate until cold and firm.
8. When ready to serve, remove the sides of the pan and invert the cake onto some parchment paper. Peel off the bottom piece of parchment paper, then invert the cake back onto a serving platter.

Make the Ganache

1. To make the chocolate ganache, put the chocolate chips in a heat-proof bowl. Microwave the heavy whipping cream until it just begins to boil, then pour it over the chocolate chips. Allow it to sit for 2-3 minutes, then whisk until smooth.
2. Spread the ganache evenly on top of the cake. Add some raspberries on top if desired and sprinkle the cake with powdered sugar. Serve with raspberry sauce if you’d like.