Here’s a gem from Charity Ferreira.
Old Fashioned Peanut Brittle
Yield: 1½ pounds of brittle
¼ cup (1/2 stick) unsalted butter, cut into chunks, plus more for pan
1 teaspoon baking soda
¼ teaspoon salt
1 tablespoon vanilla extract
2 ½ cups sugar
½ cup water
1/3 cup light corn syrup
2 cups roasted, unsalted peanuts (about 10 ounces)
Step 1: Lightly butter a 10-by-15-inch jelly-roll pan. Dissolve the baking soda and salt in the vanilla extract and set aside.
Step 2: In a large pot over medium heat, stir together the sugar, water, corn syrup, and ¼ cup butter until the sugar is dissolved and the butter is melted. Increase the heat and boil, stirring occasionally with a heatproof spatula or a wooden spoon, until the mixture turns a deep golden brown and measures 335˚F to 340˚F on a candy thermometer, 10 to 15 minutes. Remove from the heat and carefully (the mixture will bubble up) stir in the vanilla mixture peanuts.
Step 3: Immediately pour into the prepared pan. If necessary, use a spatula or wooden spoon to spread the mixture flat. Let stand at room temperature until cool and hard, about 1 hour.
Step 4: Bend the ends of the pan to release the brittle (run a spatula underneath the brittle to help release it, if necessary) and chop or break into chunks. Store in an airtight container in the refrigerator for up to 2 weeks.