Crunchy, golden peanut brittle with roasted peanuts in a caramelized shell is a nostalgic family candy-making tradition. This classic American confection is a beloved holiday gift and treat.
Line a large baking sheet with parchment paper or a nonstick baking mat and set aside.
In a heavy-bottomed saucepan over medium heat, combine granulated sugar, corn syrup, water, and salt. Stir constantly with a heatproof spatula until sugar is dissolved and mixture comes to a gentle simmer.
Attach a candy thermometer to the pot. Increase heat to medium-high and cook, without stirring, until the temperature reaches 300°F (hard crack stage), about 10–15 minutes. Swirl the pan occasionally for even cooking.
Immediately remove from heat. Quickly stir in butter and vanilla extract, then add the roasted peanuts and stir until evenly distributed and coated in caramel.
Stir in baking soda swiftly—mixture will foam—then promptly pour the hot brittle onto the prepared baking sheet. Spread thinly and evenly using a spatula. Cool completely, then break into pieces.