Pre-heat the oven to 180°C. Line the bottom of two 23cm round cake tins with baking paper and grease the sides with butter or baking paper.
In a large bowl or the bowl of a stand mixer cream the butter, sugars and eggs until pale and creamy.
Add all remaining ingredients and mix on medium-high speed for 3-4 minutes until all ingredients are incorporated.
Split the batter between the two cake tins and bake for 30-35 minutes until a toothpick inserted into the centre of the cakes comes out clean.
Remove from the oven and allow to cool in the tin before removing and frosting. If not frosting immediately, wrap the cakes and either refrigerate for a few days or freeze.
Salted caramel frosting
Add all ingredients to the bowl of a stand mixer and beat on high speed until frosting is light and fluffy.
In a small pot on the stove or a microwavable jug, heat the cream until almost boiling. Remove from the element, or microwave and add the chocolate. Whisk together until all chocolate is melted and whisk a little more until it thickens slightly. Allow to cool before pouring on cake.
To assemble the cake
Slice both cakes horizontally using a large sharp knife so that you have 4 layers.
Place one cake on a cake board or plate. Spread ⅓ of the frosting, right to the edges. Repeat with the remaining 3 cakes, leaving the top layer bare.
Pour the ganache over the whole cake allowing it to drip down the side.
Drizzle extra salted caramel sauce over the top of the cake and sprinkle with sea salt flakes.
Serve immediately or store in the fridge for up to 5 days.