Start off by melting your milk chocolate in the microwave at 30 second intervals, stirring regularly every 15 seconds to ensure the chocolate doesn’t burn. Once fully melted set aside to cool. 

Add your chilled double cream to a bowl ( it’s important that it’s very cold which ensures you get the smoothest and fluffiest mousse) with the icing sugar , vanilla, cocoa powder the cooled melted chocolate. Whisk this gently until you reach a soft ribbon consistency. It’s important not to over-whip this mixture so it’s best to whisk this by hand.

Place the chocolate mouse mixture into a piping bag (this will ensure you make as little mess as possible when assembling the cake).

Line a 900ml loaf tin with grease-proof paper or a tin which is wide enough to fit a rich tea finger in horizontally.

Using the piping bag, pipe lines of the mousse along the base of your tin, to create a mouse base layer.

Using the piping bag, pipe a line of mousse onto a rich tea finger and stand it up horizontally in the mousse base you have just piped. Pipe a layer of mouse onto another biscuit and sandwich it against the biscuit you have already stood up in the mousse (you are creating a row of sandwiched biscuits that runs down the centre of your baking tin. Repeat this to create a row of biscuit mousse biscuit mousse etc. Repeat this until you’ve reached the end of the baking tin.

Pipe the remaining mousse over the top and down the side of your tin and smooth out using a palette knife. Try to make this a smooth and level as you can as this will be the outside of your cake, you can always smooth the sides and top again with a warm palette knife once it has set and you remove it from the tin.

Place the cake in the fridge for at least 6 hours or ideally overnight for the biscuits to soften. If you would like to eat it the same day you can make it in the morning for the evening.

To top the cake whisk the chilled double cream and vanilla to a soft peak consistency and place into a piping bag with a star nozzle. 

Gently remove your cake from the tin and pop onto you desired platter or cake stand, dust the cake with some of the coca powder.

Using the piping bag decorate the top of the cake with the cream and top with some white and milk chocolate shavings or curls. Cut on a diagonal to show those beautiful layers and enjoy.