Instructions

1. Set your oven to 400°F (200°C). Line a 12-cup muffin tin with paper liners or place silicone muffin cups on a baking tray.
2. In a large bowl, combine the wholewheat flour, rolled oats, sugar (if using), baking powder, baking soda, cinnamon, and mixed spice.
3. In a separate bowl, whisk the eggs, then add the oat milk, oil, and vanilla extract.
4. If using date syrup instead of sugar, add it to the wet ingredients at this stage.
5. Pour the wet ingredients into the dry mixture. Add the grated apple and chopped chestnuts. Stir gently with a spatula until just combined — the batter should be thick and slightly lumpy. Avoid overmixing.
6. Spoon the batter evenly into the prepared muffin cups, filling each about three-quarters full. Bake for 20–25 minutes, or until golden brown and a toothpick inserted in the centre comes out clean.
7. Allow the muffins to cool in the tin for a few minutes before transferring them to a wire rack to cool completely.
8. Keep in an airtight container for up to 3 days or freeze for up to a month.