Preheat the oven to 350F/180C and butter 3 8″ cake pans and dust them with some flour to prevent the cakes from sticking.
In a large saucepan heat stout, coffee and butter together until the mixture comes to a gentle simmer. Add cocoa powder while whisking continuously to avoid lumps until smooth. Set aside to cool.
Blend flour, sugar, baking soda, and salt in a different bowl. Mix eggs, vanilla and creme fraiche with an electric mixer in bowl number 3.
Now check on your chocolate mixture and make sure it’s cool enough to continue the process.
Add the chocolate mixture to the egg and creme fraiche mixture and blend them together. Add flour mixture a little bit at a time and beat on low speed until combined. Divide batter equally among the pans.
Bake cakes in the preheated oven for 30 minutes. (I baked mine one at a time.)
Remove the cakes from the oven and cool on a wire rack. (Once cooled I usually wrap my cakes in a plastic wrap and chill my cakes in the fridge overnight.)
Make salted caramel buttercream by whipping butter in a bowl of a stand mixer until light and fluffy and then adding prepared caramel or dulce de leche with a pinch of flaky salt until completely incorporated.
Wrap honeycomb pieces in a clean tea towel and crush with a rolling pin or process in a food processor. Fold in crushed honeycomb pieces into salted caramel buttercream.
(If Carnation caramel is not available in your supermarkets you can make your own by boiling a can of sweet and condensed milk in a pot of water for 3 hours.)
Fill the cake layers with salted caramel buttercream, then cover the entire cake with a crumb layer and chill in the fridge for 30-40 minutes.
Meanwhile, make a chocolate ganache. Bring heavy cream to a boil and take it off the heat immediately, then add your chopped chocolate into it and stir until melted! Cool it and whip it with an electric mixer until paler in colour and fluffy.
Cover the chilled cake with chocolate ganache and decorate with more honeycomb pieces and flaky salt.