Instructions

1. Preheat the oven to 180C and line a medium, deep baking tray with parchment paper.
2. In a mixing bowl, mix together the dry ingredients for the base. Add the oil and milk and mix well.
3. Press the batter into the lined baking dish and put in the fridge to cool.
4. Next, make the apple filling. Peel, core, then thinly slice the apples. Put them in a mixing bowl. Sprinkle over the flour, sugar and cinnamon and mix gently until the apples are well coated. Set aside.
5. In another mixing bowl, stir together the chopped walnuts, flour, oats, sugar and cinnamon. Add the margarine and, using your hands, rub everything together until you get a mixture, resembling breadcrumbs. Set aside.
6. Take the dish out of the fridge, and arrange the apple slices evenly on top of the base. Scatter some raisins over the apple slices, if used.
7. Scatter the crumble over the filling, then gently press it down to stick to the apples.
8. Bake in the middle of the oven for 30- 35 minutes, until golden brown.
9. Allow it to cool completely before you remove it from the tray. Cut it into bars.