Add chocolate to milk and place over low flame. Cook until mixture is smooth and blended, stirring constantly.
Add sugar, salt, and corn syrup; stir until sugar is dissolved and mixture boils.
Continue boiling, without stirring, until a small amount of mixture forms a very soft ball in cold water - 232° F.
Remove from fire. Add butter and vanilla. Cool.to lukewarm - 110° F. Beat until of right consistency to spread. If necessary, place over hot water to keep soft while spreading.
Makes enough frosting to cover tops and sides of two 9-inch layers, or top and sides of 13x9x2-inch cake.
Servings: