Preheat oven to 150°C. Line a baking sheet with baking paper. Draw a 20cm circle on the baking paper. Set aside.
Whisk egg whites in an electric mixer until fluffy and voluminous (Make sure you use a large bowl for this job as the egg whites will expand). Add sugar 1 tablespoon at a time while whisking for a couple of minutes until it turns glossy, forms stiff peaks and sugar is melted (Test this by turning the bowl upside down. The mixture should stay put. Also try rubbing the mixture between your fingertips, you should hardly feel the sugar).
Add cornflour, vinegar and vanilla. Mix very briefly for 2-3 seconds (Do not overmix as this can later cause the pavlova to crack).
Mix melted chocolate and 20ml of the coffee in a small bowl. Pour this into the egg white mixture and swirl once or twice gently with a wooden spoon.
Dollop the pavlova mixture in the middle of the circle on the baking sheet. Using a wooden spoon, spread until you just reach the edges of the circle. Using a flat blade knife, structure your pavlova by drawing the knife up in furrows around the edges. Flatten the top slightly. If you’d like to fill the pavlova, make sure you create a little crater on top.
Place pavlova in the hot oven. Reduce temperature to 120°C and bake in the oven for 70 minutes. Turn off the oven and allow the pavlova to cool in it completely for a couple of hours or overnight.
Prepare the coffee cream by whisking cream and icing sugar along with 20ml of the coffee in a small bowl with an electric beater. Whisk only for about 30 seconds at which point the cream will become thick and of spreadable consistency.
Fill or top the cooled pavlova with the cream. Garnish with red berries and stone fruit. Dust with icing sugar and serve immediately.