Preheat the oven to 175°C. Grease and line three x 20cm round cake tins with baking paper.

In a bowl, sift together the flour, sugar, cocoa, baking soda, baking powder and salt. Set aside.

In a separate bowl (or a stand mixer if you have one), beat together the eggs, buttermilk, canola oil and vanilla until smooth.

Gradually add the dry ingredients to the wet ingredients on a low speed until almost combined. Add the hot coffee and mix until just combined. Gently fold in the chocolate chunks.

Divide the batter among the three cake tins (I use a cup measure to try to make it as even as possible) and bake for 20-25 minutes or until the tops are just set and a skewer comes out just clean. Remove from the oven to cool. After 20 minutes or so, remove from the tins and place cakes on cooling rakes or paper-lined flat plates to cool completely. The cakes need to be completely cool before you start frosting - normally a couple of hours.

Make the salted caramel and caramel popcorn in the few days before you assemble the cake, and make the buttercream immediately prior to assembly.

Heat the butter and cream in a small saucepan over a low heat until the butter is melted and the mixture is combined. Remove from the heat.

Place the sugar and water in a large pot over a low heat, stirring until the sugar is dissolved. Stop stirring (as it can cause the sugar to crystallise) and cook on a high heat until the mixture reaches a dark amber colour (usually about 10 minutes and when it reaches ~175°C/350°F on a candy thermometer).

Quickly whisk in the cream and butter mixture, but be careful here as it boils up vigorously with a lot of steam, so you may want to wear an oven mitt or similar to protect your hand.

Remove from the heat and add the salt and vanilla extract, stirring to combine. Leave to cool and then taste to adjust the salt.

Set aside in a jar or similar - you will be using this caramel in the popcorn, the buttercream and to drip over the finished cake.

Preheat the oven to 150°C and line a baking tray with baking paper. Make the popcorn according to packet instructions, in a popcorn machine or in a pot (see here for instructions)

Place popped popcorn in a large bowl.

Heat the caramel until almost boiling. Add the baking soda, stir as it fluffs up and quickly pour over the popcorn. Toss the caramel through the popcorn until evenly coated and then spread out over the baking tray in an even layer. Bake for 10 minutes, turning once after 5 minutes. Leave to cool. Store in an airtight container.

Using a stand mixer fitted with a paddle attachment or a handheld electric mixer, beat the softened butter until pale and creamy, about five minutes.

Add the cream cheese, caramel and vanilla and beat at low speed until fully incorporated. Gradually increase speed and continue beating until light and fluffy, scraping down the sides of the bowl with a spatula, about 3-4 minutes.

Add the icing sugar in three lots, beating on low speed until combined. Beat on medium high speed until smooth and fluffy while scraping down the sides (about 2 minutes)

Make the salted caramel and the salted caramel popcorn. Just before assembly, make the salted caramel cream cheese buttercream.

If your cakes have domed at all, cut off the top with a serrated knife to flatten.

Place the first layer, flat side up (upside-down) on a cake stand. Cut out few strips of baking paper and slide under the edges of the cake (see picture above) to catch any drips, so when you have finished icing the cake you can pull them out and end up with a clean-edged cake stand/plate.

With a knife or offset spatula, spread the top with caramel buttercream (use just under a cup, or enough to make a layer a similar size to in the picture). It doesn’t matter if the buttercream goes over the edge a little as it will be incorporated into the frosting on the sides of the cake. Place the second layer on top and spread evenly with frosting. Repeat with the third layer, but this time also frost the sides of the cake with the remaining frosting.

If you are at all worried about the structural stability of your cake (which I almost always am, when I carry it around etc!), cut 3-4 wooden skewers to the height of your cake and poke them through the three layers to stop them from sliding over each other.

Place in the fridge to set slightly while you make the chocolate ganache.

Place very finely chopped chocolate a small bowl. Bring cream to boiling point and pour over the chocolate, making sure the chocolate is all covered. Leave for five minutes then stir with a fork until smooth and glossy.

Once you have made the chocolate ganache, remove the cake from the fridge and pour the ganache over the top of the cake. Use a knife or offset spatula to spread it over the top, creating drips down the sides.

Leave to set for 10-15 minutes. At this point you can remove the baking paper strips from the cake stand.

Just before serving, stack the caramel popcorn on the top of the cake, interspersing handfuls of popcorn with drizzles of extra salted caramel to stick it all together. You will probably end up with extra popcorn.

Drizzle any extra salted caramel over the sides of the cake however you wish.

Devour!