To make the sponge layers:

To make the sponges, gently melt your chocolate in a microwave-safe bowl on a medium heat for 30 seconds at a time, stirring until just melted. This could also be done over a Bain Marie. Leave to cool while getting on with the next bit.

Preheat your oven to 160C Fan.

In a stand mixer with the paddle beater attachment, with an electric hand beater or by hand, cream the butter, sugar and vanilla paste together until pale in colour and fluffy. Start for a couple of mins on slow speed, then once the sugar is mixed in, turn up the speed to a medium/high to beat. If doing it by hand, it'll take a good 10 minutes, but hey, you're earning the calories per slice!

Reduce the speed to slow and gradually add the egg until it's completely amalgamated, occasionally scraping down the bowl's side to ensure you've got all the butter and sugar from the sides and the bottom of the bowl. Don't worry if it looks a bit curdled, this will disappear when you add the flour and cocoa.

Keeping the mixer on a slow speed, pour in the melted chocolate and mix in. If doing by hand, just mix in, in 3 or 4 increments and stir gently.

Next, add the soured cream, mixing on slow for 20 seconds or so (or stir).

Lastly, whisk the cocoa into the flour in a separate bowl to distribute it evenly. Add this to the chocolate mixture in increments of about three and gently mix on slow just until the powdery flour is mixed in. Don't overbeat, or your sponge might be heavy.

Now spoon a third of the mixture into each tin (I like to weigh mine in their tins to ensure they're all the same height and will bake evenly) and level off each with a spoon. Pop in the oven for 18-25 minutes or until JUST baked. A testing knife should come out of the centre of the sponge a little pastey, not clean, and the cakes should be shrinking away from the tin edge a bit. Check after 15 minutes to be safe as all ovens vary. Remove and cool in the tins for 10 minutes, then turn out onto a wire rack, remove the paper and leave to cool.

To make the fudge icing:

To make the ganache frosting, place the chocolate chips in a large heatproof bowl. Boil the cream and pour over the chocolate chips, then place a large plate over the bowl to trap the heat. After a few minutes, use a wooden spoon to stir in one direction to bring the cream and chocolate together. Leave to cool.

Beat the icing sugar into the cooled ganache, then add the melted butter and whisk in.

To assemble:

Place a cake onto your plate or stand and spread over a thick layer of the frosting, top with a second cake layer and repeat. Then add the last layer of cake, with the smooth side that was in the bottom of the tin uppermost. Pile on the frosting and use a palette knife to spread over the top and sides, you can leave it a fairly rough finish - just make sure the entire cake is covered with a layer of the fudge frosting.

The cake will keep well for up to 5 days in an airtight tin. It’s also lovely to slice and blast in the microwave for 10 secs or so just to gently warm and serve with a big dollop of cream or a scoop of ice cream.