Let's start with the caramel first, as it still has to cool down. Put sugar in a saucepan and let it melt over medium heat. Make sure that the sugar gets not too dark. Add butter and stir. When the butter has dissolved we add the cream. Be careful here as the caramel can splash. Stir vigorously and simmer for 1 minute while stirring. Remove from heat and set aside.
Preheat oven to 180ºc.
To make the shortbread, plain flour and caster sugar in a bowl. Rub in the softened butter, vanilla and coffee until the mixture forms a dough, then press into the base of the prepared tin.
Prick the shortbread lightly with a fork and bake for 20 minutes or until firm to the touch and very lightly browned. Leave to cool in the tin.
When the ground has cooled, add the caramel and place in the freezer for 10 minutes.
Melt the chocolate and cream slowly in a bowl over a pan of hot water. Stir coffee and pour over the cold caramel and leave to set. Cut into squares or bars.