Prepare the Cake Pan: Line the bottom of a 9-inch round cake pan with parchment paper. Grease the sides lightly with butter or non-stick spray to ensure easy removal. Set the pan aside. Preheat your oven to 355°F (180°C).
Melt Chocolate and Butter: In a double boiler (or a heatproof bowl set over simmering water), melt the chocolate chips and butter together. Stir constantly until the mixture is smooth and fully combined. Remove from heat and transfer to a large mixing bowl. Allow the mixture to cool slightly—it should still be warm but not hot.
Incorporate Egg Yolks: Whisk in the egg yolks, one at a time, into the slightly cooled chocolate mixture. Fully combine each yolk before adding the next. Set aside.
Make the Meringue: In the bowl of a stand mixer fitted with a whisk attachment, add the egg whites and coconut sugar. Beat on medium-high speed until soft peaks form and the mixture resembles a glossy meringue. This process may take about 4-5 minutes. Be careful not to overbeat, as you want soft, not stiff, peaks.
Combine Meringue and Chocolate Mixture: Gently fold the meringue (whipped egg whites and sugar) into the chocolate mixture in four increments. Start by adding about one-quarter of the meringue and folding it in to lighten the batter. Gradually fold in the remaining meringue, being careful not to deflate the air you’ve incorporated.
Pour and Bake: Pour the batter into the prepared cake pan. Smooth the top with a spatula. Place the pan on the center rack of your preheated oven and bake for 30 minutes. Use a food thermometer to ensure the internal temperature reaches 200°F (93°C) for the perfect fudgy texture. (you could use a spring-form pan if you wanted to)
Cool the Cake: Remove the cake from the oven and let it cool in the pan for 20 minutes. Once cooled slightly, gently loosen the edges with a knife. Place a serving platter over the top of the pan, then carefully flip the pan and platter together to release the cake. Peel off the parchment paper. The bottom of the cake will now be the top.
Prepare the Chocolate Ganache Glaze (Optional): While the cake cools further, prepare the ganache. Heat the heavy cream in a small saucepan over medium heat or in the microwave until it is steaming but not boiling. Pour the cream over the chocolate chips in a heatproof bowl. Let it sit for 3-5 minutes, then stir until the mixture becomes smooth and glossy.
Decorate with Ganache: Pour the ganache over the top of the cake, using an offset spatula to spread it evenly over the surface and edges. Allow any excess to drip down the sides for a dramatic effect. Alternatively, you can dust the cake with powdered sugar for a simpler finish.
Chill and Serve: Chill the cake in the refrigerator for at least 2 hours to set the ganache. If you’re short on time, you can serve it immediately after decorating. Slice and serve with a scoop of homemade or store-bought vanilla ice cream, a dollop of whipped cream, and fresh raspberries or strawberries for a stunning presentation.