Add the salt and ginger and pour it into a shallow dish and let it cool in fridge. When the cupcakes have cooled, pour half the caramel into a piping bag and pipe some caramel sauce inside each ...

Take the pan off the heat and stir in the rum and ginger syrup until the sauce is smooth. Leave the caramel to stand for 15–20 minutes, or until it cools enough to coat the back of a spoon ...