Put the oat milk, egg yolks, banana, oats, baking powder and vanilla in a blender and process to as smooth a mixture as you can get. Whisk the eggs whites until they hold stiff peaks. Whisk 1-2 tbsp of the whites into the batter, then fold in the rest.
Heat a non-stick pan over a medium heat and spray with a whisper of oil, pour about 2 tbsp of batter into the pan and cook for 1-2 mins, until the base sets and bubbles appear all over the top. Flip and cook the other side for a minute. Repeat in batches, making sure the top looks dryish before attempting the flip, or the centre will collapse.