Sunken Black Forest Cake

1.Heat butter and chocolate together until about 75% melted in the microwave. Stir until it’s finished melting and is smooth. Let it cool while you prepare the rest of the cake.
2.Heat your oven to 350°F. Coat the bottom and sides of a 9-inch springform pan with nonstick cooking spray and line the bottom with a circle of parchment paper. Set it aside.
3.Place egg whites in the bowl a stand mixer fitted with a whisk attachment. Beat on medium-high speed until they’re foamy, then slowly pour in the lemon juice and half the sugar, continuing to beat until the egg whites are billowy and almost glossy and hold a soft peak. Try not to overbeat them until they’re stiff and tight foam-looking; it leads to more dry cakes. Scrape them into a separate bowl.
4.Place the egg yolks, remaining sugar, and salt into the empty used bowl and beat on medium speed until thick and pale yellow, about 1 to 2 minutes.
5.With the mixer running, slowly pour in the chocolate-butter mixture, and mix well. Use a rubber spatula to fold one-third of the beaten egg whites into the chocolate cake batter to lighten in.
6.Fold half the remaining egg whites in carefully, then the second half. Fold them into the batter by cutting your spatula downward through the middle of the bowl, scraping it along the bottom of the bowl, and then pulling the mixture back up, folding them with the batter.
7.Transfer batter to prepared cake pan and smooth the surface. Bake until the center is puffed up, and just barely firm/dry to the touch, and a toothpick inserted into the center comes out with just a few dry crumbs clinging to it, about 35 to 40 minutes. Try not to overbake it, the chocolate at the edges will smell toasty or that cake can taste dry at the edges. Place the cake on a wire rack to cool completely; it will sink in the center.
8.Once cake is completely cool, beat the heavy cream, 2 teaspoons caster sugar, and vanilla together until medium peaks form. In a small bowl, combine combine the preserves and kirsh.
9.Use a knife to loosen the edges of the cake from the pan and invert it onto your rack. Peel off parchment paper, then invert it back onto a serving plate. Spoon the whipped cream into the center and then the preserves mixture on top. Cut into wedges and serve. You may also serve the preserves on the side.