Rub together the butter and flour until the mixture forms large crumbs. It is important to use hard fat to get a firm crumb.
1. Mix in the remaining crumble ingredients.
2. Put half or slightly more than half of the mixture into the Swiss roll tin and spread it evenly.
3. Press down evenly, use your fingers.
4. Peel, core and grate the apples.
5. Mix with the sugar, cornflour, raisins and spices.
6. Spread this over the mixture in the tin.
7. Top with the remaining crumble mixture and pat down lightly.
8. Dot the top with flakes of the butter and bake at 180°C/350°F/Gas Mark 4 for 45 mins.
9. Remove from oven and mark out slices with a sharp knife.
Once cool break along the lines.