Many brittle connoisseurs use raw nuts, which cook in the syrup; others prefer the roasted kind. For a delicious variation on this recipe, stir in ½ cup raw cacao nibs along with the peanuts.

Have ready a marble slab or a large baking sheet lined with buttered parchment paper or a silicone liner and set on a wire rack. Combine in a large heavy saucepan:

Bring to a boil over medium-high heat, stirring until the sugar is dissolved. Boil, without stirring, to 265°F, the hard-ball stage. Stir in:

Continue cooking, stirring as seldom as possible and only to prevent hot spots from burning, until the syrup reaches 300°F, the hard-crack stage. Remove from the heat and stir in:

As soon as the butter is melted and incorporated, turn out onto the slab or baking sheet. Place a silicone liner on top, put oven mitts on your hands, and press the brittle to the thickness of one nut. Allow to cool completely. Break the brittle into pieces, then store between layers of wax or parchment paper in an airtight container at room temperature for up to 1 month.