Start by lining a 20cm square tin with non-stick paper and grease lightly with oil. This will prevent the caramel from sticking. Next, make the caramel. Place the sugar and water into a large clean frying pan and cook for approx. 10-12 minutes until the sugar goes a light golden colour (DO NO TOUCH) To stop the caramel from continuing to cook, place the pan into another pan filled with water. Quickly stir the nuts into the caramel to coat completely and spoon into the prepared tin, evening out with the back of a spoon. Allow to cool down, then melt the chocolate and pour over to coat the top and sprinkle over some coarse salt. Allow to set completely for 1 hour before cutting up into small fingers.