03For the chocolate filling, combine the chocolate, espresso and corn syrup in a medium bowl. Place the heavy cream in a small saucepan and bring just to a boil. Pour the cream over the chocolate mixture and stir gently in the same direction (do not beat), until the chocolate is melted and the mixture is smooth. Stir in the butter until it is melted.04Pour the mixture into a cup with a spout and fill the tarts to the rims. Use a knife tip to pop surface bubbles. Clean the knife and use it to cut out and lift fragments of gold leaf, and place one in the center of each tart. Let the tarts set, about 1 hour. Serve or store in an airtight tin up to 2 days.