Directions

1. Preheat the oven to 180°C/160°fan/Gas 4

2. Grease and line an 18 x 28cm (7 x 11in) cake tin
3. Put 110g (4oz) butter in a bowl with 75g (3oz) sugar and beat until smooth
4. Stir in the vanilla and gradually mix in the flour and baking powder to make a crumbly mixture
5. Press the mixture over the bottom of the tin to cover it evenly
6. Prick with a fork then chill for 30 minutes
7. Bake the base for 25 minutes until set and lightly golden

8. Meanwhile, peel, core and thinly slice the apples and mix with the lemon juice, cinnamon and sultanas and put to one side

9. In a saucepan, melt the remaining butter and sugar together with the syrup. Stir in the oats and mix well

10. Drain the apple slices and spread out evenly over the cooked base
11. Spoon over the oaty topping to cover the apples and gently press down with the back of the spoon
12. Stand the tin on a baking tray and bake for about 1 hour until the apple filling is cooked through and the top is golden and crisp
13. If the top browns too quickly, cover the tin with foil
14. Leave to stand for 15 minutes to firm up before slicing into 15 pieces

15. Serve warm with custard. To serve cold, leave to cool completely before removing from the tin.