2 cups granulated sugar
1 cup light corn syrup
1/2 cup water
1 cup butter
3 cups cashews
1 teaspoon baking soda

In a large saucepan, combine sugar, corn syrup, and water. Cook over medium heat, stirring, until sugar dissolves. Bring to a boil; blend in butter. Begin to stir frequently when syrup reaches the thread stage, about 230°. When temperature is 280°, or soft-crack stage, add cashews. Stir constantly until hard-crack stage, o300°, is reached. Remove from heat and quickly stir in baking soda. Mix well. Pour onto two buttered baking sheets or jelly roll-size baking pans. As the candy cools, stretch it out thinner by lifting and pulling at edges with forks. Loosen from the pans as soon as possible and turn over. Break hardened candy up and store in an airtight container.
Makes about 2 pounds of cashew brittle.

Source: http://southernfood.about.com/od/candyrecipes