I followed this recipe strictly.
Fresh blueberries 150g
1. Preheat oven to 180 degree C.
2. Mix flour and sugar in a bowl. Cut in butter.
3. Rub them with fingers till become coarse crumbs.
4. Press 2/3 crumbs into baking pan. Sprinkle blueberries over crumbs.
5. Spread the rest crumbs on the top also with a little extra white sugar.
6. Bake for 30 mins.