Preheat the oven to 180C/160 Fan. Line a 12 hole cupcake/muffin tin and set aside.
Peel and dice the apples and set aside.
To make the crumble, mix together the flour, sugar and oats. Rub the butter into the mixture with your fingertips until the mixture resembles breadcrumbs. Set aside.
To make the muffin batter, whisk together the flour, baking powder, cinnamon and sugar until well combined.
Add the wet ingredients and the apples and mix well.
Spoon half of the batter into each muffin case and add 1 tbsp of custard into the centre. Cover with the other half of the batter. Sprinkle over the crumble mixture onto the top of each muffin and bake for 20-25 minutes.
Notes
These muffins will last for 2-3 days in an airtight container Use a good quality ready-made custard such as Ambrosia