Peanut Brittle is a type of confection consisting of flat broken pieces of hard sugar candy embedded with peanuts.
A mixture of sugar and water is heated to the hard crack stage and to a temperature of approximately 300 °F (149 °C). Some recipes call for ingredients such as corn syrup and salt in the first step. Peanuts are mixed with the caramelized sugar. At this point spices, leavening agents, and often peanut butter or butter are added. The hot candy is poured out onto a flat surface for cooling, traditionally a granite or marble slab. The hot candy may be troweled to uniform thickness. When the brittle cools, it is broken into pieces. - from Wikipedia