Fudge à la Louise

Combine sugar, dark sweet chocolate, and milk in a heavy-bottomed saucepan over medium heat. Stir constantly until the mixture reaches a rolling boil and the chocolate is fully dissolved.

Stop stirring once the mixture boils. Clip a candy thermometer to the side of the pan and allow the mixture to cook undisturbed until it reaches 238°F (soft-ball stage).

Remove the saucepan from heat and add butter and vanilla. Do not stir; allow the mixture to cool to approximately 110°F without disturbance.

Begin stirring the cooled mixture vigorously with a wooden spoon until it loses its shine and becomes thick and creamy, which signals the onset of crystallization.

Fold in the nuts until evenly distributed throughout the fudge mixture.

Pour the fudge into a parchment-lined 8x8-inch pan, pressing it gently into an even layer. Allow it to set at room temperature for at least 2 hours before cutting into squares.