In a medium-sized saucepan, combine the granulated sugar, unsweetened cocoa, and whole milk. Stir them together until well mixed.

Place the saucepan over medium heat and bring the mixture to a boil, stirring constantly to prevent it from burning.

Once boiling, reduce the heat to low and let it simmer without stirring until it reaches the soft ball stage (when a small amount of the mixture dropped into cold water forms a soft ball).

Remove the saucepan from the heat and add the unsalted butter and pure vanilla extract. Do not stir yet.

Let the mixture cool for a few minutes until it reaches room temperature.

Once cooled, add the salt and stir vigorously until the mixture thickens and loses its gloss.

Pour the fudge into a greased square dish and let it cool and set for several hours.

Once set, cut the fudge into squares and serve. Enjoy the velvety texture and rich flavor of this classic treat!