For the Cake: Firstly, pre-heat the oven to 180C and grease and line three 8" baking pans. In a small bowl, sift together the flour, cocoa powder, baking powder, bicarb and salt. Then set aside until needed.
Using a hand mixer beat together the oil and sugar for about two minutes. With the mixer still running, add the eggs, egg yolk, vanilla and almond extract ensuring you scrape down the sides to incorporate all the mixture. On a low speed, add the flour mixture in three batches, alternating with the milk, beginning and ending with the flour mixture. Again, ensure you scrape down the sides to incorporate all the mixture. Remaining on a low speed, stream in the coffee until just combined.
Evenly divide the batter between the three prepared pans. Bake in the oven for 23-25 minutes until a skewer comes out clean and the sponges bounce back. Let them cool on a wire rack in the pans for at least 10-15 minutes, before removing them from the pans to completely cool.
For the salted caramel: While the cakes are cooling begin making the salted caramel drizzle by placing the sugar, golden syrup and water in a heavy-bottomed pan and stir to combine.
Heat over a high heat, occasionally swirling the pan, until it turns a medium gold amber colour - this will take about 10 minutes. Once the caramel starts to deepen in colour, remove the pan from the heat. Slowly and carefully whisk in the cream, the mixture will bubble up so stand clear and keep stirring.
Add the butter, whilst continuing to stir until melted. Then add the salt and vanilla to combine, I added around 4 large pinches. Pour into a heat-safe container (a pyrex bowl, jug or a jam jar will do) and set aside to cool and thicken.
For the frosting: Put the unsalted butter into a large bowl and using a hand mixer beat for a good 6 minutes, until it is super creamy. Then slowly add the icing sugar in batches, beating continually with the hand mixer until all incorporated. Add the milk and vanilla extract, and continue beating with the hand mixer until it is super light and fluffy.
For the assembly: Place one sponge onto your cake stand and using a palette knife spread a layer of frosting on top. Repeat this with the next two layers. Frost the entire cake with the remaining buttercream, and then using a cake scraper or a palette knife drag it around the cake to achieve a smooth finish, removing any excess buttercream.
Finally, pour the salted caramel over the top of the cake, coaxing it to slowly drip over the sides.