Line an 8-in. square pan with foil and grease the foil with 1-1/2 teaspoons butter; set aside. In a heavy saucepan, combine sugar, cocoa and salt. Stir in the milk until smooth; bring to a rapid boil over medium heat, stirring constantly. Cook without stirring until a candy thermometer reads 234° (soft-ball stage). Remove from the heat; add vanilla and remaining butter (do not stir).
Cool to 110° (about 5 minutes). Beat with a spoon until fudge thickens and just begins to lose its gloss. Immediately spread into prepared pan. Cool. Using foil, lift fudge out of pan. Discard foil; cut fudge into 1-in. squares.
Chocolate Fudge Tips
What is the secret to making creamy fudge?
The secret for how to make fudge super creamy is the cooling step. This step is crucial because it is when your fudge crystallizes (in this case crystallization is a good thing!) and forms its creamy consistency.
Chocolate fudge lasts for up to two weeks when wrapped in aluminum foil or parchment paper and stored in an airtight container at room temperature. If you'd like to keep it for even longer, place the wrapped fudge in the refrigerator for up to three weeks.
Research contributed by Christina Herbst, Taste of Home Assistant Digital Editor