Serves 20
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For the sponges:

For the buttercream:

To decorate:

  1. Preheat the oven to 180°C/160°C fan/gas mark 4. Line three 18cm cake tins with nonstick parchment paper.
  2. In a large bowl, beat together the butter and sugar until light and fluffy. Add the eggs one at a time, beating after each addition. Add the vanilla and mix to combine.
  3. In a large bowl, sieve together the flour, baking powder, bicarbonate of soda and salt.
  4. Stir the flour mixture into the butter mixture. Add the buttermilk, one third at a time, mixing after each addition.
  5. Divide the batter evenly amongst the prepared cake tins. Bake for 25-30 minutes or until a skewer inserted in the centre comes out clean. Allow to cool completely.
  6. In a large bowl, beat together all of the ingredients for the buttercream until smooth. Add a splash of milk if the icing is too thick.
  7. Once the sponges are cool, cut each sponge in half horizontally.
  8. To assemble the cake, place the first sponge layer on a cake stand or serving plate. Spread over some of the buttercream and add the next sponge on top. Continue to stack and spread each of the sponges.
  9. Use a palette knife or offset spatula to spread the buttercream over the top and sides of the cake, making sure to fill in any gaps. Refrigerate the cake for 30 minutes to set.
  10. Once set, spread over more buttercream to cover any crumbs and smooth the icing. To get the groove effect, glide a cake comb through the buttercream on the outside (this is optional; you could also use the back of a fork if you're patient with it!). Allow the cake to set in the fridge for 5-10 minutes.
  11. To decorate the cake, warm the salted caramel slightly and spoon into a piping bag. Snip a small hole in the end of the piping bag and add drips of caramel around the top edge of the cake; you can also use a teaspoon to make the small drizzles.
  12. In a bowl, toss the popcorn together with enough of the remaining salted caramel sauce to coat. Stir in some caramel pieces. Pile the popcorn over the top of the cake and finish with a sprinkle of cinnamon.

Nutrition Facts

Per Serving: 478kcals, 21.9g fat (0.75g saturated), 70.6g carbs (51.6g sugars), 5.1g protein, 1g fibre, 0.206g sodium