In a small saucepan heat chocolate and milk on low, stirring until melted. Add sugar, syrup and salt and cook to 236 degrees F. Add butter and pour off into a bowl to cool. Add vanilla extract and beat with a paddle attachment until it starts to lighten, lose its gloss and thicken. Pour into a greased 8-by-8-inch pan and let cool. Cut into cubes.
Recipe courtesy of Gale Gand