Mix the berries, orange zest and a squeeze of juice, vanilla seeds, sugar and cornflour in a large bowl.
Spoon into small, ovenproof dishes.
For the crumble, mix sugar, buckwheat and ground almonds in a bowl. Use your fingers to rub in the butter, until large crumbs form.
Sprinkle the fruit with the crumble and bake for 30 mins.