Preheat oven to 160°c - 320°f. Grease and line a 28cm x 18cm baking pan with parchment paper.
In a mixing bowl, combine the base ingredients together, mixing well to form a pastry consistency. Add the base mixture to the prepared baking pan and evenly spread with the back of a spoon. (See video for notes). Bake in the preheated oven for 14 to 15 minutes or until golden brown on top. Remove and let cool for 20 minutes.
Reduce oven temperature to 140°c - 280°f.
Place a small saucepan over medium-low heat, add in all the caramel filling ingredients. Mix to combine and allow the butter to melt, stirring the whole time. Once melted stir continuously for 4 minutes or until the edges of the saucepan start to simmer. Remove from the heat.
Pour the hot caramel sauce over the cooled base and evenly spread it out completely covering the base. Bake in the reduced temperature oven for 10-12 minutes or until golden and bubbly, rotating halfway through. Remove and let cool for 15 minutes before placing it in the fridge for 30 minutes to 1 hour to completely cool.
Once set, place another small saucepan over medium-low heat, add in the chocolate ganache ingredients, mixing well until it's melted and smooth. Remove from the heat. Pour the melted smooth chocolate over the set caramel and evenly spread, completely covering the surface. Sprinkle with sea salt flakes and place into the fridge to set for 1 hour, up to 24 hours.
Remove from the fridge and let sit for 10 minutes before serving. To serve, run a knife under hot water and dry it off (this will make it easier and cleaner to slice. Slice into 12 to 24 pieces and serve.