1 c. sugar
1/2 c. cocoa
1/4 c. water
1 tbsp. butter
13 oz. can unsweetened condensed milk

Stir together the sugar, cocoa, water and butter. Boil for 5 minutes, stirring constantly. Then add very slowly so as not to stop boiling, the can of milk. Mixture will thicken as you add the milk. This will keep in the refrigerator for a long time. Just warm for hot fudge sundaes.