- Preheat the oven to 400°F (200°C) and line a muffin tin with paper liners.
- Whisk the yogurt, milk, maple syrup, oil, eggs and vanilla together in a large bowl. In a separate bowl, stir together the whole wheat and all-purpose flours with the baking powder, baking soda, cinnamon and zest (if using). Add the dry ingredients all at once to the liquids and stir with a wooden spoon or spatula just until blended (a few lumps are OK). Stir in your additions.
- Scoop or spoon the batter into the muffin cups, filling them almost to the top. Sprinkle lightly with turbinado sugar if you wish. Bake for about 25 minutes, until a tester inserted in the centre of a muffin comes out clean. Cool the muffins in the pan on a cooling rack for at least 20 minutes.
- To serve, turn out the muffins onto a platter and enjoy warm or at room temperature. The muffins will keep in an airtight container at room temperature for up to 4 days, or can be frozen for up to 6 months.