Preheat the oven to 180°C/350°F/Gas mark 4. Grease and line two 20cm/8in round tins.

Sift the flour, cocoa powder, baking powder, and bicarbonate of soda into a bowl, then stir in the sugar.

In a separate bowl, whisk the eggs, buttermilk, oil, and vanilla extract together. Pour into the dry ingredients and beat until smooth and combined.

Add the hot coffee a little at a time until combined. Divide the batter between the tins.

Bake for about 35-55 minutes, checking after 35 minutes. A skewer inserted in the center should come out clean or with a few moist crumbs.

Once baked, cool the cakes completely in their tins on a wire rack. Wrap the cakes and refrigerate overnight or for at least one hour.

To make the salted caramel, combine the sugar and water in a saucepan, boil without stirring until amber. Remove from heat and carefully add the cream.

Return to medium heat and whisk until smooth. Add salt to taste and let cool completely.

For the buttercream, whisk egg whites and sugar over simmering water until warm and sugar dissolved. Transfer to a stand mixer and whisk until thick and cool.

Gradually add the butter to the meringue, whisking until smooth. Add vanilla extract and salted caramel.

Slice each cake in half to create four layers. Spread buttercream and salted caramel between the layers.

Apply a thin crumb coat of buttercream on the outside of the cake and refrigerate for 15 minutes.

To make the ganache, heat the cream, pour over chopped chocolate, and let it sit before stirring until smooth. Allow it to cool to room temperature.

Whisk the ganache until lightened, then quickly spread over the cake.

Drizzle remaining salted caramel on top of the cake.