Mocha layer cake

To make the chocolate cake, preheat the oven to 170°C/gas mark 3. Grease and line the bases of two deep 6 inch/15cm cake tins with baking parchment and set aside

Place the cacao powder, vanilla bean paste, espresso and boiling water in a bowl and mix until completely combined

Place the softened butter and caster sugar in the bowl of a stand mixer and beat them together until pale and creamy. You may need to scrape the sides of the bowl down to make sure they are mixed evenly

Add the eggs to the butter mixture a little at a time and beat between each addition until combined. It may look a little gloopy, this is fine. When all of the eggs have been added, scrape in the chocolate mixture and beat well to combine

Add the salt, baking powder and a third of the flour to the mixing bowl. Beat to combine, scraping down the sides as necessary. When all of the flour has been mixed in, add another third of the flour and half of the milk. When fully mixed add the remaining flour and milk and mix to combine. Sprinkle in the cacao nibs and stir so they're evenly distributed

Divide the mixture evenly between the two cake tins, smooth the tops so they are as even as possible and bake in the preheated oven for 60 minutes or until a skewer comes out clean. When cooked, leave the cakes to cool completely in their tins, then turn them onto a wire rack, removing the greaseproof paper from the bottom

To make the buttercream, place the chocolate in a bowl and melt together over pan of simmering water. Set aside to cool to room temperature

Beat the butter until very pale and fluffy, add the icing sugar and beat until combined. Add the melted chocolate and beat for another 2 minutes or until very fluffy

Take the cooled cakes and trim the tops to make them flat. Cut each cake in half so you have four layers of cake. Place a blob of buttercream on a plate or cake stand to secure the sponge and put the first layer of cake on top of it. Spread a thin layer of buttercream over the top

Repeat with the other layers of cake, ensuring the final top surface is flat and smooth. Spread a thin layer of buttercream on the outside of the cake and the top, you will still be able to see the cake through the buttercream. This is known as a 'crumb coat', which will provide a nice base for the final layer of icing

Place the cake in the fridge for 30–45 minutes to firm up. When the icing is firm, spread the rest of the icing evenly over the cake, reserving a little so that you can pipe blobs on top to decorate

Return the cake to the fridge and make the glaze by adding the butter and chocolate to a saucepan and heating gently until they both melt and mix together. Then stir in the coffee and allow the glaze to cool to room temperature

Using a spoon, trickle the glaze over the edge of the cake so it drips down and then pour the remainder of the glaze over the top of the cake so that the top is covered

Take the remaining buttercream and place it in a piping bag fitted with a French tip. Pipe a ring of blobs around the edge of the cake and sprinkle the top with cacao nibs to finish