- Preheat oven to 350°F. In large bowl, whisk egg. Add mix and butter; stir vigorously until smooth.
- On 17x11-inch foil-lined, greased, rimmed baking sheet, place dough in center. Cover with wax paper; press into 15x10-inch rectangle. Carefully remove wax paper.
- Bake 16-18 minutes. Cool 10-15 minutes; invert to remove foil. Cool completely; break or cut into pieces.
Makes about 13 servings.
Tip: For crispier brittle, bake an additional 2-3 minutes.