Combine butter, sugar, and water in a large, thick bottomed saucepan over medium heat, stirring frequently until the butter has melted and everything starts to combine. Continue to cook, stirring frequently, almost constantly, until thermometer reaches 300°F and the toffee has turned a golden brown, almost peanut butter color, about 10-15 minutes. Remove from heat and immediately stir in almonds, vanilla extract, baking soda, and salt.
2 cups salted butter, 2 cups granulated sugar, 2/3 cup light brown sugar, 1/4 cup water, 2 teaspoons vanilla extract, 3/4 cup toasted almonds, 1/2 teaspoon baking soda, 1/2 teaspoon salt