Preheat oven to 350 degree F. Grease and flour an 8x8x2-inch baking pan; set aside. In a large bowl combine cake mix and brown sugar; add almond butter or peanut butter. Beat with an electric mixer on low speed just until crumbly. Set aside 1/3 cup of the crumb mixture. Add the water and egg to remaining crumb mixture; beat on low speed for 30 seconds, scraping side of bowl constantly. Beat on high speed for 2 minutes. Stir in 1/4 cup of the almond toffee pieces. Pour into prepared baking pan.
Bake in preheated oven for 20 minutes. Stir remaining 1/4 cup almond toffee pieces and the almonds or peanuts into the reserved crumb mixture; carefully sprinkle over cake. Bake for 10 to 20 minutes more or until a toothpick inserted into center comes out clean. Cool in pan on wire rack. Makes 8 servings.