Step 1

Combine the evaporated milk, brown sugar, butter, and salt in a heavy-bottomed medium saucepan. Place over medium heat and bring to a boil, stirring until smooth. Continue to simmer, stirring frequently, until a candy thermometer reaches 238°F (see Notes).

Step 2

Remove from heat and pour into a heat-proof bowl. Add the vanilla and combine with a hand-held mixer. Add the powdered sugar in small additions while continuing to beat with the mixer. Mix until smooth. Add the walnuts and mix until just combined.

Step 3

Spread the fudge into an ungreased 8-inch square pan (line with parchment or wax paper if you like). Let cool completely, about 1 hour, or chill in the fridge for 30 minutes. Slice with a sharp knife. Store fudge in an air-tight container for several days.