Line a baking sheet with parchment paper. Set aside.
Gather and portion out all ingredients carefully to avoid possible burning during cooking time.
In a 2-quart saucepan over medium heat, bring sugar, corn syrup, salt, and water to a boil. Stir until sugar is dissolved.
Add nuts and stir until combined.
Put a candy thermometer into mixture and continue cooking, stirring constantly, until temperature reaches 300°F.
Immediately remove saucepan from heat, and quickly stir in butter, vanilla extract, and baking soda.
Immediately pour mixture onto prepared baking sheet.
Use a rubber spatula to spread mixture out on the sheet as evenly as possible.
Cool brittle completely at room temperature.
Snap candy into pieces and serve as desired. Store in an airtight container at room temperature.