Put the flour and baking powder into a bowl and rub in the cubes of butter, using your fingers until you have a mixture like coarse sand.
This is such a small amount, it's not really worth getting out the heavy machinery.
Stir in the sugar and then put into a freezer bag to freeze. This mixture is enough to make 4 jumbleberry crumbles in the cups (as in the photo).
Preheat the oven to 220°C/200°C Fan/gas mark 7/425ºF. Put the summer fruits in either a cup or ramekin and sprinkle the cornflour and sugar over the top. Stir around a little.
Sprinkle approx. 75g /½ cup of the frozen crumble topping over the fruit and bake the cup for 20 minutes.
