Using a large mixing bowl, combine together the flour, baking powder, cinnamon and salt.
In a separate blow, whisk together the sugar with softened butter, then add the egg, milk and vanilla essence.
Stir the grated apples to the egg mixture.
Pour the wet batter into the dry ingredients, stirring slowly, until just combined. Don't overmix it at this stage.
Spoon the muffin batter into 12 large muffin cases or greased and lined large muffin tin.
Mix together the remaining sugar and cinnamon to make the streusel topping and sprinkle it on to the muffins.
Bake in preheated oven (180C or 370 F) for about 20 minutes, until the top of the muffins spring back when lightly touched and wooden skewer comes out clean.