1. Preheat the oven to 325 F and line a 9″ springform pan with parchment paper. Grease the entire pan with non-stick spray.
2. In the bowl of a stand mixer fitted with the whisk attachment, or using a handheld mixer, mix the 8 eggs on HIGH for 6-7 minutes, or until the volume has increased substantially and they’re light and fluffy.
3. Add the chocolate and the butter together in another microwave-safe bowl. Put the bowl in the microwave and heat on high for 30 seconds at a time, stirring in between, until everything is smooth and melty.
4. Using a spatula, fold half of the whipped egg mixture into the melted chocolate, folding until thoroughly combined. Fold in the remaining egg mixture, again folding with the spatula gently, until the mixture is consistent and smooth. Pour it into the prepared pan and smooth the top out with your spatula. Bake the cake for 40-45 minutes, or until the cake doesn’t jiggle in the center when given a slight shake. Remove the pan from the oven and allow it to cool completely, about 1 hour, before wrapping it in plastic wrap and placing it in the fridge for 3-4 hours.
5. When ready to serve, run a knife along the outer edge of the cake, then release the cake from the pan. Invert the cake on to a plate or parchment to remove the bottom layer of parchment, then flip back over and prepare for serving, with berries, powdered sugar, or whipped cream. Enjoy!

Leftover cake keeps well in the fridge for 3-4 days, or up to 2 months in the freezer, in an airtight container.