How to make Liam Charles' toffee apple crumble layer cake

"It is pretty evident I am obsessed with apple crumble," says Liam Charles, the stand-out contestant of last year's Great British Bake Off.

"This cake has four layers of light brown sugar sponges, apple compote filling, and squiggles of salted caramel. And a few clusters of crumble, you know, for texture, as they say," he adds.

Ingredients:

(Serves 16-24)

For the sponge:

750g unsalted butter, softened

600g golden caster sugar

150g light muscovado sugar

12 large eggs

750g self-raising flour

1tsp baking powder

180ml whole milk

1/2tsp vanilla extract

For the crumble:

225g plain flour

135g soft brown sugar

1tsp fine sea salt

150g unsalted butter, cold and cubed

For the cinnamon buttercream:

900g unsalted butter, softened

1.95kg icing sugar

2tsp ground cinnamon

180ml whole milk

11/2tsp vanilla extract

For the filling and topping:

350ml shop-bought salted caramel

Apple compote

Apple crisps (optional)

You will need 4 x 25cm cake tins

Method:

1. Preheat oven to 180C/Gas 4 and grease and line the cake tins.

2. Make the cakes. Cream your butter and both sugars together in a large bowl with a freestanding or hand-held mixer until light and fluffy. Crack the eggs in one at a time, mixing after each addition. If the mixture begins to curdle, just pop in a couple of tablespoons of the flour to bring it back together. Turn the speed down very low and add your flour and baking powder. Finally, add the milk and vanilla and give it one more blast. Divide your mixture evenly between the cake tins and bake for 25-30 minutes, or until a skewer inserted into the middle comes out clean. Remove from the oven and allow to cool for 10-15 minutes in the tins before turning out on to a wire rack.

2. Make the crumble. Line a baking tray with baking paper. Tip your flour, sugar and salt into a large bowl and give it a good mix. Take the cubes of butter and begin to rub them into the flour. Tip the crumble onto the baking tray and bake for 25-30 minutes, until deep golden brown. Remove from the oven and leave to cool. Smash it and tip into an airtight container, ready for later.

3. Make the buttercream. Measure your butter into a large bowl and beat with your free-standing or hand-held mixer until light and pale. Sift your icing sugar and cinnamon into a separate bowl, then add it to the butter in three stages, beating after each addition. Scrape down the sides of the bowl from time to time. Add your milk and vanilla to loosen the buttercream and give it one more mix.

4. Use a cake leveller or sharp knife to trim the top off all the cakes so they are level. Spread a small amount of buttercream on a board that is slightly bigger than your sponges and place your first layer of sponge on top. Place that board on a turntable, if you have one. Place half the buttercream in a piping bag, snip the end and pipe a circle around the edge of the first layer of sponge, leaving a 10cm circle in the middle. Fill that circle with apple compote and sprinkle with crumble. Spoon the caramel into a piping bag and cut the tip off, then squiggle the salted caramel on top.

Repeat until all the sponges are stacked. Your last sponge should be placed upside down on top.

5. Using a palette knife, cake scraper and a turntable, coat the outside and top of the cake with a thin layer of the remaining buttercream. Place in the fridge for at least an hour to set.

6. Remove the cake from the fridge and apply another layer of buttercream around the sides and top of the cake. Use any leftover buttercream to pipe around the top edges of your cake. Finally, place apple crisps on top with more crumble and - yes - more salted caramel.

Cheeky Treats by Liam Charles, photography by Haarala Hamilton, is published by Hodder & Stoughton, priced £20. Available now.