Put the oats, blackberries, eggs, vanilla, almond milk, ground almonds and baking powder in a blender. Pulse until you get a thick but pourable mixture. Add more almond milk if the mixture is too thick.
Heat your waffle maker.
Spoon some batter into the waffle maker, spreading it out evenly. Close the top and cook for 3-5 minutes (depending on your machine).
When the waffle is golden, move to a plate and make more waffles using up the batter. You should get about 4 waffles, depending on your machine.
Meanwhile, make the compote. Put the blackberries into a small pan, then add the sugar and vanilla extract. Cook for about 5 minutes until the liquid becomes syrupy (but it should not turn into a jam!)
Serve the waffles with the compote.