Hazelnut Brittle
Adapted from "The Martha Stewart Living Cookbook," it contains 4 ingredients: sugar, water, apple cider vinegar and hazelnuts. While the original doesn't specify a temperature to cook it to, a recommendation is to cook it to a hard crack stage. You may substitute other nuts if desired.

4 c sugar
1 c water
1/4 t apple cider vinegar
5 1/2 c hazelnuts, lightly toasted

Combine sugar, water and vinegar in a medium saucepan over medium heat. Cook until amber in color, about 20 minutes, brushing the sides when necessary to avoid crystallization. Add in the nuts. Pour onto an oiled 12x17 inch pan and set until firm but soft enough to cut. Invert onto a cutting board and unmold. Using a large oiled chef's knife, cut the rectangle into even pieces. Alternatively, pour over buttered surface, let cool and break into irregular pieces.

Recipe adapted from:

Martha Stewart Living, ed. The Martha Stewart Living Cookbook. New York: Martha Stewart, 2000.