Mix all the base ingredients in food processor until sticking together.
Line a 22cm x 26cm with baking paper.
Press the base mixture into the baking paper lined tin and cook for approximately 25 minutes until tinged golden on top.
While the base is cooking, make the caramel. Stir butter, brown sugar, sweetened condensed milk and golden syrup over a low heat until sugar is dissolved.
Bring to the boil and boil for 7 to 10 minutes, stirring the whole time. The caramel should be a rich golden colour.
Take caramel off the heat and add vanilla essence. Beat well.
Pour caramel onto shortbread base and set in fridge (approx 2 hours).
Once caramel is set, melt the chocolate and spread over caramel. Cut into pieces almost straight after you've spread the chocolate, as the chocolate will set quickly on the cold caramel and if you try and cut it once the chocolate has set, the chocolate will crack.