Old Fashioned Cocoa Fudge

3 cups sugar
2/3 cup cocoa
1/8 teaspoon salt
1-1/2 cups milk
1/4 cup butter or margarine
1 teaspoon vanilla extract

Line 8 or 9 inch square pan with foil; butter foil. In large heavy saucepan stir together first three ingredients; stir in milk, with a wooden spoon*.

Cook over medium heat, stirring constantly, until mixture comes to a full rolling boil. Boil without stirring, to 234 degrees F. on a candy thermometer. (or until syrup, when dropped in very cold water forms a soft ball which flattens when removed from water.) Remove from heat. Add butter and vanilla. DO NOT STIR! Cool at room temperature to 110 degrees F (lukewarm). Beat with wooden spoon until fudge thickens and loses some of its gloss. Quickly spread into prepared pan; cool. Cut into squares. Store wrapped loosely in foil in the refrigerator.

*it is very important not to use a wire whisk or anything like that. Also just stir gently, even though the cocoa will stay floating on top, it will mix in as the mixture heats up.