1.Preheat oven to 120°C. Line an oven tray with baking paper. Mark an 18cm (7¼-inch) circle on paper.
2.Place chocolate in a small heatproof bowl over a small saucepan of simmering water (don’t allow bowl to touch water); stir until just melted. Cool slightly.
3.Beat egg whites in a small bowl with an electric mixer until soft peaks form; gradually add caster sugar, beating until dissolved after each addition, and mixture is thick and glossy.
4.Fold cornflour and vinegar into meringue mixture; swirl in chocolate. Dollop meringue inside marked circle on tray.
5.Bake meringue for 1 1/4 hours or until dry to the touch. Turn oven off, leave meringue to cool in oven with door ajar.
6.Meanwhile, make cherry blueberry compote: Place cherries, blueberries, sugar and the water in a medium saucepan over medium heat; bring to a simmer. Simmer for 5 minutes or until cherries and blueberries have released juices. Using a slotted spoon, transfer cherries and blueberries to a small bowl. Stir jam into juices in pan; bring to the boil. Boil for 5 minutes or until mixture thickens. Pour syrup over cherry mixture. Cool completely.
7.Beat cream cheese, extract and icing sugar in a small bowl with an electric mixer until smooth; gradually beat in cream until smooth and combined.
8.Just before serving, spoon cream cheese mixture on pavlova; top with compote. Decorate with fresh cherries.
Make ahead: The pavlova can be made a day ahead; store in an airtight container at room temperature. Topping is best made close to serving. To check that you have beaten the meringue sufficiently, rub a little of the mixture between your fingers it should feel silky smooth, without any grainy sugar crystals.