Chocolate Peanut Toffee

Directions

1. 1
   Butter baking pan and put on a heatproof surface.
2. 2
   Bring butter, sugar, and salt to a boil in a 4- to 5-quart heavy pot over medium-high heat, whisking until smooth, then boil, stirring occasionally, until mixture is deep golden and registers 300°F (hard-crack stage; see Kitchen Notebook, page 240) on thermometer, 15 to 20 minutes.
3. 3
   Immediately stir in whole peanuts, then carefully pour hot toffee into center of baking pan. Spread with spatula, smoothing top, and let stand 1 minute, then immediately sprinkle chocolate on top. Let stand until chocolate is melted, 4 to 5 minutes, then spread over toffee with cleaned spatula. Sprinkle evenly with chopped peanuts, then freeze until chocolate is firm, about 30 minutes. Break into pieces.