If your peanut brittle is chewy, it is most likely because it did not reach the required heat level before you took it off the burner. In order to achieve a peanut brittle that is firm and cracks under pressure, you need to achieve the hard-crack temperature stage. This is roughly 350 degrees Fahrenheit. You can use a candy thermometer to test your brittle if you'd like. Your peanut brittle also may not be brittle if you skip baking soda.u003cbr/u003e