Knead the flour, oat flakes, sugar, cinnamon and butter to make crumbles. Wash the blueberries, drain them and cover with 1 1/2 tablespoons of flour in a bowl.
Mix the flour, sugar, baking powder, baking soda and salt well in a bowl. In another bowl, mix the buttermilk, olive oil, eggs and vanilla sugar together. Slowly stir in the flour mixture. Finally fold in the blueberries.
Pour the batter into muffin molds and spread the crumble on top. Bake the whole thing at 200 ° C for about 25 minutes.