This mouthwatering brittle is featured in the Butterscotch Cream Pie recipe from "The Craft of Baking," by pastry chef Karen Demasco.
Lightly coat a rimmed baking sheet with nonstick cooking spray; set aside.
In a large saucepan, combine sugar, butter, corn syrup, and 1/2 cup water; stir so that sugar is wet. Place mixture over high heat and cook, without stirring, until it turns dark amber in color, about 10 minutes. Remove from heat.
Carefully whisk in baking soda, followed by salt; mixture will rise and bubble. Using a wooden or metal spoon, fold in cashews. Pour mixture onto prepared baking sheet, spreading in an even 1/2-inch-thick layer using back of the spoon. Let cool completely.
Break brittle into bite-size pieces using a mallet or the back of a heavy knife. Brittle can be stored in an airtight container at room temperature, up to 2 weeks.