Stir the apple cider vinegar into the soy milk and leave for 5 minutes to curdle slightly; this makes a vegan buttermilk.
In a bowl, whisk the oat flour, protein powder, baking powder and ground flaxseed.
Pour in the soy milk mixture and vanilla and stir until just combined. Lumps are fine; overmixing makes them tough. Rest 5 minutes.
Heat a large non-stick skillet over medium-low heat for 2 minutes and coat lightly with cooking spray.
Pour in 60 ml (1/4 cup) portions and cook until bubbles appear and the edges look dry, about 2 minutes. Flip and cook 1 minute more until golden and cooked in the centre. Repeat with the rest of the batter.
Serve stacked with blueberries and maple syrup.
Tips
Plant protein makes batter thicker; add a splash more milk if needed.