Preheat the oven to 300 degrees F. Line a large-rimmed baking sheet with a nonstick silicone mat and lightly butter.
In a heavy-bottom saucepan, combine the sugar, water, and corn syrup. Bring to a boil over medium heat; boil until it registers 230 degrees F on a candy thermometer, about 10 minutes. Transfer the almonds to the oven on another large-rimmed baking sheet until warmed through, but not toasted.
When the syrup reaches 239 degrees F, stir the almonds into the syrup with 1 teaspoon salt. Continue cooking, stirring occasionally, until the syrup is 300 degrees F and a rich caramel color; immediately stir in the butter, vanilla, and baking soda.
Pour the brittle mixture onto the prepared baking sheet, folding the border back towards the middle to distribute the heat evenly. Cool completely at room temperature and break into pieces.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of Tell Tale Preserve Co., 2011