Old Fashioned Hershey Cocoa Fudge

3 cups of sugar
2/3 cup cocoa
1/8 teaspoon salt
1 1/2 cups whole milk, no substitute
1/4 cup real butter, no substitute
1 teaspoon vanilla extract
Line 8 or 9-inch square pan with foil; butter foil.
In a large heavy saucepan stir together the 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). Bulb of candy thermometer should not rest on the bottom of the pan. (This can take 20-30 minutes).
Remove from heat. Add butter & vanilla.
DO NOT STIR! Cool at room temperature to 110 degrees F (lukewarm). (This can take 2 to 2-1/2 hours).
Beat with a wooden spoon until fudge thickens & loses some of its gloss. (This can take 15-20 minutes. It really works best if you have someone to ‘tag-team’ with.) It starts to look more like frosting than a thick syrup when it is ready.
Quickly spread into prepared pan; cool.
Cut into squares.
Enjoy