For the Bark:
For the Caramel Sauce:
First make the caramel sauce. In a medium, heavy-bottomed saucepan dissolve the sugar and water over medium-low heat. Stir until the sugar has dissolved then increase the heat to high. Every so often swirl the pot to keep the mixture moving. It will start bubbling. Once it has darkened to a medium amber color, remove from the heat and immediately add the butter and cream to the pan (it will bubble up a lot) and whisk violently until combined and smooth. Stir in vanilla extract. Set aside to cool.
To make/assemble the bark, line an 8x8" pan with parchment paper leaving some overhang to pull the bark out with. Blitz the chocolate in a microwave-safe bowl in 30 second increments stirring after 1 1/2 minutes and watching carefully until melted and smooth (do NOT overheat...stir to make sure you really still need to melt the chocolate further, sometimes the residual heat will melt any lumps you do see). Pour half the chocolate into the pan and spread or tip to smooth. Sprinkle some or all of the shortbread over the chocolate and press gently down. Transfer to the freezer for 5-10 minutes to harden. Then remove from the freezer and pour the caramel sauce on top spreading until an even layer. Sprinkle with coconut and press into the caramel gently. Return the pan to the freezer to harden further for 5-10 minutes. Remove from freezer and top with the remaining chocolate. drizzle with caramel sauce and sprinkle with coconut. Harden further in the fridge but bring the bark more to room temperature before cutting with a sharp knife so it doesn't splinter. Keep refrigerated until ready to serve.