Bring butter, liquids, syrup, instant espresso, and salt to a boil. Add chocolate, cover, and remove from heat. Let stand about 5 minutes, or until chocolate is soft. Stir, until cool and thickened. Set into cold water to hasten process. If it gets too firm, reheat and cool again.
Put cake on wire cake rack, set on a cooky sheet, and pour all the frosting on