Preheat the oven to 190ºC, 375ºF. Grease a muffin tin or line it with paper cases.
In a large bowl, sift together the flour, baking powder, sugar and cinnamon. In another bowl, combine the milk, apple juice, egg and butter.
Pour the wet ingredients in to the bowl of dry ingredients and stir until just combined. Be careful not to overstir - this batter has quite a thick consistency as the apple will give out juices as it cooks. Add the chopped apple and stir again once or twice.
Spoon the batter in to the muffin tins and bake for twenty to twenty-five minutes until brown. Remove from the oven and allow to cool in the tin.