The best simple to make Old-fashioned Southern Peanut Brittle to date.
Measure the pure vanilla into a small bowl and set it aside. Combine the natural baking soda and kosher salt in another small bowl and set aside. Butter metal baking sheets with sides or unsalted butter. Set aside until needed.
Combine the granulated sugar, light corn syrup, and ½ cup water in a large heavy-bottom saucepan. Bring the mixture to a boil, then attach the candy thermometer and cook over medium-high heat until the syrup spins a thread when poured from a spoon or reaches 250° degrees F° on the candy thermometer. Stir in the unsalted peanuts or pecans and continue cooking and stirring until the candy becomes golden brown or reaches 300 degrees F°
Remove the mixture from the heat immediately and quickly add the 1 stick butter and the pure vanilla, natural baking soda, and kosher salt. Stir only until the butter melts, and then quickly pour the peanut brittle onto the pretreated metal sheet, spreading the mixture thinly. When the brittle has completely cooled, break the candy into pieces and store in a tightly covered container.