This dense and fudgy "kladdkaka" is the first cake that Aquavit chef Emma Bengtsson learned to make when she was a child in Sweden with her grandmother. The same recipe is on the menu today at Aquavit!
Preheat the oven to 325 degrees F. Melt butter in a medium saucepan over medium heat. Meanwhile, sift the flour and cocoa powder through a fine-mesh sieve onto a sheet of parchment, to remove any lumps. Set aside. Crack the eggs into a bowl; add the sugar and whisk well to combine. As soon as the butter has melted, add the chocolate; stir with a wooden spoon to combine as the chocolate melts, about 3–5 minutes.
Add the flour and cocoa mixture to the eggs, little by little, stirring well between additions to prevent lumps. Once the batter is well mixed and smooth, add the melted butter and chocolate; stir well to combine. Spray the bottom and sides of a springform pan with nonstick spray and line the bottom with parchment paper. Pour in the batter; place in the oven to bake, 20–25 minutes.
Cake is done when a tester inserted into the center comes out clean. Cool the cake before removing from pan, 10–15 minutes. (Note: In the meantime, make the whipped cream. In a stand mixer fitted with a whisk attachment, whip heavy cream on medium speed, 30 seconds. Turn to high and whip until medium peaks form, 1 minute.) When cake has cooled, cut into slices and garnish with whipped cream, fresh berries, and a dusting of confectioner’s sugar before serving.