Instructions

1. Preheat the oven to 350 degrees F. Generously butter the inside of a 9-inch springform pan. Sprinkle the pan with roughly 2 tablespoons of granulated sugar and turn the pan around so the sugar can evenly coat the buttered interior. Set aside.
2. Place the chopped 8 ounces of chocolate and ½ cup butter in the top of a double boiler and melt until smooth. Mix occasionally to combine. Allow to cool slightly, until just warm to the touch.
3. Place the egg whites in a medium bowl. Place the yolks in a slightly larger bowl. Using a handheld mixer, beat the whites on medium speed until glossy stiff peaks form, about 2 minutes. Next, add the cup of sugar to the bowl with the egg yolks, then beat on medium speed until the mixture become thick, fluffy and pale; roughly 2 minutes.
4. Pour the melted chocolate and butter into the egg yolk mixture. Using the handheld mixer, beat to combine. Add the potato starch and salt and beat again until just combined. In 3 batches, fold the whipped whites into the chocolate base with a rubber spatula. Carefully fold it until just combined, being careful to try and not smash the egg whites.

5. Pour the mixture into the prepared pan and bake until puffed and crackly on top, about 33 to 35 minutes. Be careful to not overbake. Cool completely on a wire rack.

6. To make the whipped cream, Add the cold heavy whipping cream, sugar and vanilla to a large bowl. Using the cleaned handheld mixer, beat on high until soft peaks form - be careful to not overwhip. Set aside or cover and refrigerate until ready to use.
7. When the cake has cooled, run a thin knife around the edge of the pan to release the cake and remove the outside ring. If the cake is completely cooled, you can lift it off the bottom piece of the springform pan using a metal spatula and set on a plate or platter. Dust the top with confectioners' sugar, and serve the individual slices with a dollop of whipped cream.