MAKES ABOUT 1½ LB.
- 3 oz. unsweetened chocolate, finely chopped
- 4 tbsp. unsalted butter, plus more for greasing
- 1 (1-lb.) box confectioners' sugar, sifted
- ½ cup plain mashed potatoes
- 2 tsp. milk
- 1 tsp. vanilla extract
- ⅛ tsp. kosher salt
- ½ cup finely chopped walnuts
Place chocolate and butter in a heatproof bowl set over a saucepan of simmering water. Cook, stirring occasionally, until melted, 3-5 minutes. Remove bowl from pan and let cool slightly. Stir in sugar, potatoes, milk, vanilla, and salt until dough forms. Using hands, knead dough briefly in bowl until smooth. Press into a greased 8” square pan; sprinkle with the chopped walnuts. Chill fudge 1 hour before cutting into squares.