Preheat oven to 350°. Line 9x13 inch baking pan with aluminum foil, allowing at least 1 inch excess on each 9 inch side. Lightly grease bottom only.
In a large bowl, combine brownie mix, eggs, water and oil. Using a wooden spoon or spatula; mix well, do not beat.
Spread 1/2 the batter evenly into prepared pan.
Unwrap candy bars and arrange in single layer, with space between each bar, crosswise on top of batter. Do not let candy bars touch side of pan.
Carefully spoon remaining brownie batter over candy bars to edges of pan.
Bake 40 minutes or until toothpick inserted near center comes out with only a few moist crumbs on it.
Remove pan from oven. Let cool on wire rack.
Using edges of foil as handles, remove to cutting board. Cut into squares. Serve with vanilla ice cream or whipped cream if desired.