Preheat the oven to 180°C conventional (160°C fan-forced). Grease or line a 12-hole muffin tin.
In a large bowl, combine the wholemeal flour, rolled oats, ground flaxseed, baking powder, bicarbonate of soda and salt.
In a separate bowl, whisk together the eggs, milk, olive oil, maple syrup and vanilla.
Pour the wet ingredients into the dry ingredients and stir until just combined.
Fold through the dark chocolate chips. Allow the batter to rest for 5 minutes so the oats and flaxseed can absorb some moisture.
Divide the batter evenly between the muffin holes.
Bake for approximately 20–25 minutes, or until golden and a skewer inserted into the centre comes out clean (avoiding a melted chocolate chip).
Allow to cool before serving. Store in an airtight container for a few days or freeze individually for easy snacks.