1. Lightly butter a large baking sheet or line it with a silicone baking mat. Measure the vanilla and baking soda ahead of time so they are ready when needed.

2. In a heavy saucepan, combine the granulated sugar, light corn syrup, water, and butter over medium heat. Stir until the sugar dissolves and the butter melts.

3. Once the mixture begins to boil, stir in the peanuts and continue cooking, stirring often so the nuts toast evenly and the candy does not scorch.

4. Cook until the mixture reaches 300°F on a candy thermometer and turns a deep golden color.

5. Remove the pan from the heat and quickly stir in the salt, vanilla extract, and baking soda. The mixture will foam up and become lighter in texture.

6. Immediately pour the brittle onto the prepared baking sheet and gently spread it into a thin layer with a buttered spatula.

7. Let the brittle cool completely at room temperature until firm, then break it into pieces and serve or store in an airtight container.