Step 1

Line a rimmed baking sheet with a silicone baking mat or parchment paper that has been coated with non-stick cooking spray; set aside.

Step 2

In a medium saucepan, combine sugar, water, corn syrup and salt. Bring to a rapid simmer over medium-high and cook until deep golden, about 20 to 25 minutes. Remove pan from heat. Stir in butter, baking soda, and peanuts (mixture will foam). Stir until mixture is no longer bubbling and caramel is smooth, 1 minute.

Step 3

Transfer to the prepared baking sheet and quickly spread with a lightly greased spatula. Let cool until firm, about 15 minutes. Break into pieces. The brittle can be stored in an airtight container at room temperature for up to 3 weeks.