To make old-fashioned peanut brittle, gather granulated sugar, water, light corn syrup, butter and roasted peanuts. The recipe also calls for baking soda and a candy thermometer.
In a large pan, combine 2 cups of granulated sugar, 1 cup of light corn syrup and 1/2 cup of water. Cook this mixture over medium heat, stir and wait for the sugar to dissolve. Once again, bring the mixture to a boil, then add 1 cup of butter. Bring all the ingredients to boil, then stir the mixture frequently when the syrup begins to thread, at about 230 degrees Fahrenheit.
When the temperature of the mixture is about 280 degrees Fahrenheit, known as the soft-crack stage, add 3 cups of dry roasted peanuts. Keep stirring until the mixture reaches 300 degrees Fahrenheit, or the hard-crack stage. Remove from the heat, and quickly stir in 1 teaspoon of baking soda.
Pour the mixture onto two buttered baking sheets or pans. As the peanut brittle begins to cool, stretch it out across the pan by pulling and lifting the edges with forks. As soon as possible, loosen the peanut brittle from the pan and turn it over. Break the peanut brittle into smaller pieces, and store it in an airtight container. This recipe makes about 2 pounds of peanut brittle.