Line a baking sheet with foil; butter foil. Set aside.Advertisement
Butter side of a heavy 2-quart saucepan. In the saucepan, combine brown sugar, milk, and salt. Cook over medium-high heat about 5 minutes or until boiling, stirring constantly with a wooden spoon. Avoid splashing mixture on side of pan. Carefully clip candy thermometer to side of pan.
Cook over medium-low heat, stirring frequently, for 18 to 20 minutes or until thermometer registers 236 degree F (soft-ball stage). Remove the saucepan from heat. Cool without stirring about 50 minutes or until mixture is lukewarm (110 degree F).
Remove candy thermometer. Beat candy vigorously with a wooden spoon until penuche just begins to thicken. Add nuts. Continue beating penuche until it's very thick and just starts to lose its gloss (about 10 minutes total). Quickly turn onto prepared foil-lined baking sheet. Let candy harden (45 to 60 minutes). Break or cut into pieces. Store tightly covered. Makes about 1 pound.