In a large saucepan mix the following:
1 c. sugar
1/3 c. milk
5 T. butter
Cook, stirring often until this comes to a full boil. Stir constantly on the heat for 60 seconds. Remove from heat and stir in quickly until just melted....
1/2 t. vanilla
1 c. chocolate chips
Pour IMMEDIATELY over cake and hurry up.. It sets up in about 2 minutes or less....