Sift the flours, baking soda, baking powder, cinnamon and salt, if using. Set aside.<br></br>

Preheat the oven to 190 C and line 12 muffin moulds with liners (see notes).<br></br>

In a mixing bowl, beat the butter and sugars with a hand mixer, till pale and fluffy.<br></br>

Add the egg and vanilla, beat to combine.<br></br>

Now add a spoonful of the flour mixture, then half the yoghurt. The flour stops the batter from curdling because of the yoghurt. Beat lightly, then add a little more flour mixture and the rest of the yoghurt.<br></br>

Now slowly fold in the remaining flour mixture, then fold in the diced apples.<br></br>

Divide the batter equally among the muffin moulds and bake for 20 minutes until a toothpick poked in the center comes out clean. About 5 minutes before the muffins are done, sprinkle on a bit of brown sugar over the tops, then put them back in the oven to finish baking. This is just for a little extra crunch and sparkle, totally optional.<br></br>

For a little extra colour on the tops, turn your oven to the broil setting for 2 to 3 minutes, or bake at 200 C for 2 to 3 minutes towards the end of the baking time.<br></br>

Allow the muffins to cool for 10 minutes, then place on a wire rack to cool completely. Store in an airtight tin at room temperature for 2 to 3 days, or in the fridge for a week. These muffins can be frozen for a month. Happy baking!