- Unsalted butter, room temperature, for baking sheet
- 1 1/2 cups sugar
- 3/4 cup cold water
- 1/2 cup light corn syrup
- Pinch of salt
- 2 1/2 cups unsalted dry-roasted peanuts
- 1 teaspoon pure vanilla extract
- 1 teaspoon baking soda
- Vegetable oil, for spatula
Butter a 9-by-13-inch rimmed baking sheet; set aside. In a medium saucepan, bring sugar, water, corn syrup, and salt to a boil over medium-high heat, stirring until sugar has dissolved.
Continue cooking, without stirring, until mixture reaches the soft-ball stage on a candy thermometer (238 degrees to 240 degrees), swirling pan occasionally; wash down sides of pan with a pastry brush dipped in water to prevent crystals from forming. Stir in nuts, and continue cooking, stirring frequently to prevent nuts from burning, until mixture is light amber.
Remove pan from heat; carefully stir in vanilla and baking soda (mixture will foam up in pan). Pour onto prepared baking sheet; quickly spread into a 1/2-inch-thick layer with an oiled metal spatula. Let stand until completely cool.
Break brittle into large pieces.