Preheat your oven to 350°F. Prepare a 9-inch springform pan by lining the base with parchment paper and lightly greasing the sides with cooking spray. If you don’t have a springform pan, use a regular cake pan with parchment paper overhanging the sides for easy removal.

Chop the chocolate into small pieces and combine with the butter in a large, heatproof bowl. Melt the mixture in the microwave, stirring at short intervals, until fully combined and smooth. Stir in the Chambord or your chosen flavoring. Allow the chocolate mixture to cool to room temperature but not so long that it begins to solidify.

Using a stand mixer or hand mixer, whisk the egg yolks until they start to thicken. Gradually add 1 ounce of sugar and continue whisking until the yolks reach the ribbon stage shiny and able to drip down in a ribbon-like stream.

In a separate clean bowl, beat the egg whites and salt on medium speed until they form very soft, foamy peaks. Gradually add the 4 ounces of sugar, a little at a time, while continuing to whip. Increase the speed and whip until you achieve soft to medium peaks that are smooth and hold their shape, but not stiff or clumpy.

Fold the whipped egg yolks gently into the cooled chocolate mixture using a large spatula or bowl scraper. Be careful to preserve as much air as possible. Add a small amount of the whipped egg whites to the chocolate mixture and fold it in to lighten the texture. Then, carefully fold in the remaining egg whites, ensuring no streaks of white remain.

Pour the batter into the prepared springform pan, smoothing the surface if necessary. Place the pan in the center of the oven and bake for approximately 40 minutes. Avoid opening the oven door during baking to prevent temperature fluctuations. When done, a skewer inserted into the center should come out clean.

Allow the cake to cool in the pan on a wire rack for about an hour. During this time, the cake will naturally deflate, developing a mousse-like interior and a beautifully cracked surface. Once cooled, carefully remove the springform ring.

Place the chopped chocolate in a heatproof bowl. Heat the heavy cream in the microwave until it is hot but not boiling, and pour it over the chocolate. Push the chocolate pieces under the cream’s surface and let it sit undisturbed for 5 minutes.

Whisk the mixture gently until it becomes smooth and glossy. If lumps persist, microwave the ganache in 30-second intervals, whisking after each session. Stir in Chambord or vanilla extract. For an ultra-smooth ganache, you can use an immersion blender to eliminate any remaining lumps.

Pour the ganache over the cake, letting it cascade over the edges naturally. Allow the ganache to set slightly before decorating with fresh berries or your preferred garnish.

Store the cake at room temperature for up to five days. After slicing, wrap any leftovers in plastic wrap to keep them from drying out. For longer storage, freeze the cake for up to one month.