First things first, preheat the oven to 180°C/160°C Fan/Gas Mark 4. Grease and line a 9” square tin. For the crumble topping, place the butter and light brown sugar in a large bowl and beat together until creamed.
Pop in the flour and mix together to create a crumble mixture – this can be done by hand or in a mixer. Finally stir in the crushed biscuits and set your crumble mixture aside.
For the filling, peel and core the apples, then chop into small chunks and place in a large bowl. Pour the lemon juice into the bowl and toss the apples in it – this prevents the apples from browning. Sprinkle the corn flour and cinnamon over and mix through.
Next up the sponge base, pop the butter and sugar into a bowl and cream together until smooth. Add the eggs and Vanilla Extract and beat together until smooth – if the mixture begins to curdle add a spoonful of flour. Sieve over the flour and Baking Powder and fold through until just combined.
Pour the sponge mixture into your prepared tin and smooth to evenly cover the base. Dollop 25g of biscoff spread on top and swirl through the sponge mixture using a cocktail stick. Spread the apple on top to create an even layer, sprinkle over the White Chocolate Chunks and drizzle over the remaining biscoff spread – you might need to heat the spread in the microwave for 10 seconds so it’s runny enough to drizzle. Finally sprinkle on the crumble topping to cover the filling.
Pop your crumble cake into the oven and bake for 60 minutes, the crumble topping should be golden brown. Your crumble cake is delicious served warm with a drizzle of biscoff spread on top and a dollop of ice-cream or custard for a tasty dessert!