Classic chocolate layer cake with lime and chocolate mousse

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Rukmini Iyer creates a decadent chocolate mousse layer cake, zested up with lime for a wonderful citrus kick.

First published in 2015

This cake – as with so many interesting dishes - came about as the result of a happy culinary accident. I had grand plans for it to become a dark, towering, glossy affair, referencing the cake that Bruce Bogtrotter manfully chomps his way through in Roald Dahl’s ‘Matilda’. But, with the chocolate, double cream and lime poised by the stove and ready to turn into a deep, rich ganache, I spotted a couple of spare eggs, and started to think – what the hay, I always make lime ganache - but what about a chocolate mousse? So, with a little trial and error, this home-made and infinitely more grown up version of a Sara Lee gateaux emerged instead. Despite its beguilingly light and airy look, you’ll find the cake quite rich – one to serve in delicate slivers rather than big wodges.

For the all-important cake base, the best way to get a good hit of chocolate flavour, without drying out the cake, is to replace a quantity of the flour with an equal weight of cocoa powder, instead of adding the cocoa powder on top of the classic flour-sugar-butter ratio. This principle works with all types of chocolate cake, so the multipurpose recipe below will work for tray-bakes, cupcakes or a layer cake.




Chocolate cake

  • 225g of butter
  • 225g of caster sugar
  • 4 eggs
  • 195g of self-raising flour
  • 30g of cocoa powder
  • 1 tsp baking powder
  • 50ml of milk

Chocolate lime mousse


  • 20cm cake tin 2


Preheat your oven to 180°C/gas mark 4
Beat the butter and sugar together until pale and fluffy, then one-by-one, beat in the eggs until smoothly incorporated
In another bowl, mix together the flour, cocoa powder and baking powder. Tip this into the butter and egg mixture and fold in gently until smooth. Stir through the milk, then divide the batter equally between the two cake tins
Transfer the tins to the oven and bake for 20–25 minutes until the tops are firm, and a skewer inserted into the middle of the cakes comes out clean. Allow the cakes to cool for 5 minutes in the tins before turning out onto a wire rack to cool down completely
Once cool, carefully slice the cakes in half horizontally and place the least good-looking layer on a cake plate or stand
For the mousse, place the chopped chocolate and lime zest in a heatproof bowl set over a pan of boiling water, making sure that the bottom of the bowl doesn’t touch the water
Place on a low heat and stir constantly until the chocolate is melted. Take the bowl off the heat and allow the chocolate to cool down for a few minutes. Meanwhile, whisk the double cream with an electric whisk until it forms soft peaks
Beat the two egg yolks into the chocolate – don’t panic if it looks like it has seized into an unmanageable lump – once you start incorporating the cream, it’ll settle down
Take two large tablespoons of the whipped cream and beat them thoroughly into the chocolate and egg mixture to lighten it, before gently folding through the rest of the whipped cream
Working as quickly as you can, spread a thick layer of mousse onto the first layer of cooled cake, making sure not to spread the mousse quite to the sides. Place another layer of cake on top, and press down gently, then repeat until you’ve got four layers of cake and four layers of mousse, with one as the topping
If not eating immediately, refrigerate the cake until needed, and eat within two days
First published in 2015

Having left a career as a lawyer to pursue her foodie passions, Rukmini went on to work at Tom Kitchin's The Kitchin in Edinburgh. She is now a food stylist, food writer and recipe developer based in London, and is the author of The Roasting Tin.

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