Grease a gratin dish with a little oil and sprinkle with 3 teaspoons of ground hazelnuts.

Mix the flour, sugar, 100 g ground hazelnuts and cinnamon in a bowl. Add the margarine in small pieces and rub everything together with your hands until it forms coarse crumbs.

Spread the blueberries in the prepared dish and cover evenly with the crumble.

Bake the blueberry and hazelnut crumble in the oven at 200 degrees (top and bottom heat) for about 20 minutes until golden brown.