Preheat the oven to 190°C (170°C fan, gas mark 6).
Mix the dry ingredients together and cut in the butter. Rub the butter into the dry ingredients until it resembles a crumble mix.
Whisk the egg, milk, vanilla extract and grated apple together in a separate bowl.
Mix the wet ingredients with the dry until just incorporated.
Pour the batter into a lightly greased mini muffin tin and bake at 190°C for 10-15 minutes until slightly golden.
Once baked, dip the muffins in melted butter then roll in the cinnamon sugar mixture.