This flourless, gluten-free cake will cave in at the centre to create a lovely, fudge-like hollow to load with traditional black forest sour cherries, chocolate and real whipping cream.
Lightly spray an 8-inch (2 L) springform pan and line bottom with parchment paper; set aside. Preheat oven to 350°F (180°C).
In a bowl over saucepan of hot water, melt chocolate and butter together. Let cool slightly.
In another bowl, whisk whole eggs with half of the sugar until it starts to thicken. Whisk in chocolate mixture and vanilla.
In a separate bowl, use a mixer on low or a whisk to beat egg whites until soft peaks form. Gradually beat in remaining sugar. Fold some of the egg whites into chocolate mixture and then fold in remaining whites until no streaks remain.
Pour into prepared pan and bake for about 30 minutes or until top puffs and starts to crack and centre is no longer wobbly (centre will still look wet).Let cool completely in pan on rack (centre will fall and sides will remain higher). Run knife around edge and release sides carefully. Place on cake plate.
Meanwhile, in a saucepan, bring cherries, juices, sugar and cornstarch to a simmer over medium heat. Cook for about 2 minutes or until thickened. Remove from heat and let cool.
Whip cream, then spoon jarred cherries into centre of cake and top with the whipped cream. Sprinkle with shaved chocolate and garnish with fresh cherries if desired.