Preheat the oven to 170C, Gas Mark 3
Line a 23cm baking tin with baking parchment
In a bowl rub together the flour, caster sugar and 200g of butter until the mixture forms a ball. It will still be crumbly. Press the mixture into the baking tin.
Prick the dough with a fork and place in the oven.
After five minutes lower the temperature to 150C, Gas Mark 2 and cook for 30 minutes until golden.
Leave the shortbread to cool in the tin.
To make the caramel melt 115g of butter in a pan.
Add the rosemary, golden syrup and condensed milk and bring to a simmer, stirring all the time.
Simmer for around ten minutes until the mixture thickens being careful it doesn't burn.
Pour the caramel over the shortbread and leave to cool.
Place the chocolate in a microwaveable bowl and heat in the microwave for 1 - 2 minutes until melted, stirring part way though. If you don't have a microwave melt the chocolate in the bowl placed in a pan of boiling water. Pour over the top of the caramel and put in the fridge to set.