Preheat the oven to 180°C.
Mix the egg powder with the water until you get a smooth paste.
In a large bowl mix the flour, baking powder, cinnamon, sugar and oats.
Add the egg paste, grated apple, vanilla and oil, then stir. Add the hazelnut milk gradually until you get a smooth, not-too-thick batter.
Spoon the batter into a muffin tin, lined with paper cups or into individual silicon cups.
Bake the muffins for 20-25 minutes, until golden, then rest them on a tray for 5 minutes, then move them to a wire rack to cool completely.