1. Preheat the oven to 190/170C fan. Grease the Bundt cake tin with butter. Mix together two tablespoons of cocoa, one tablespoon of flour and two teaspoons of caster sugar in a bowl and then sprinkle over the inside of the Bundt cake tin so that there is an even dusting all over. Tip out any excess.
2. To make the cake, sift the flour, sugar, cocoa powder, bicarbonate of soda and salt into a large mixing bowl or into the bowl of a stand mixer.
3. Add the butter, then mix until the butter is combined and the mixture resembles breadcrumbs.
4. Stir in the hot coffee, yogurt and vanilla to the flour mixture, mixing until smooth. Add the whisked eggs and mix until combined.
5. Pour the batter into the cake tin. Tap on the counter to eliminate any bubbles.
6. Bake the cake for 55 minutes. Check the cake is cooked by testing with a skewer that comes out clean when inserted into the cake.
7. Cool the cakes for 20 minutes in the tin, and then carefully remove the cake from the tin, onto a cooling rack.
8. To make the yoghurt frosting, add the ingredients in a bowl and mix until well combined and smooth.
9. To make the salted caramel, add the sugar, butter, double cream, salt and vanilla into a small saucepan and melt together slowly. Bring to the boil and cook at a simmer for about 5-8 minutes or until thickened. Stir through the chestnuts and popcorn so they are well coated then leave to cool for at least 30 minutes.
10. Transfer the yoghurt frosting into a piping bag, (you can also use a spoon) and spread over the top of the cake. Follow with the salted chestnut and popcorn caramel.