Number of People
Preheat oven to 200°C/fan 180°C/gas 6. Place baking tray in the oven to get hot. Butter insides of 4 large ramekin dishes (8.5 cm diameter) or 6 small ramekins. Coat each with 1 tsp caster sugar.
Gently simmer blackberries in a saucepan until the fruits are soft and mushy. Mix cornflour with 1½ tbsp cold water until smooth. Add to blackberries and stir over heat until thickened. Sieve into a large bowl. Cool.
Fit whisk in bowl, add egg whites and caster sugar. Process at speed 7 for 6 min until stiff. Using a spatula gently fold egg white mixture into cooled blackberry purée until well combined.
Fill ramekins with mixture level to the edge. Smooth the top and clean the edges of ramekins. Bake on hot baking tray 8-10.