Preheat the oven to 355F / 180C / 160 fan. Place the flax and 20ml of oat milk in a small bowl. Stir to combine and leave to rest for 5 minutes.
Toss the blueberries in a little of the flour. This will help prevent the blueberries bleeding too much.
Add all the remaining dry ingredients (except the blueberries) to a mixing bowl. Stir to combine with a spatula. Add the wet and stir until it forms a smooth batter. Stir through 40g of blueberries.
- Pour the batter into a 25 x 17 x 2.5 cm baking tray lined with greaseproof paper and add the remain-ing 20g of blueberries to the top. Bake for about 25 - 30 minutes, or until golden and you can insert and remove a skewer without crumbs sticking. Leave to cool in the tray for 10 minutes then lift onto a wire wrack to fully cool. Slice into 24 squares