Preheat oven to 180°C fan.
See video for details of how to make crumble at the start.
Muffins - add very soft butter, custard, vanilla and eggs to a bowl and use a whisk to bring together well
Add flour, baking powder, spice and sugar to a separate bowl, mix well then add the apple and mix again.
Add the custard mix to the dry mix and combine.
Fill the muffin cases with this mix then top with the crumble - you'll have extra of that which you can store in the freezer.
Bake for 25-30 minutes or until a skewer comes out clean.
