1 (21.5-oz) package brownie mix
plus additional ingredients listed on the package - eggs, water, vegetable oil
3 (6-oz) king-sized Symphony chocolate bars with toffee and almonds, unwrapped
Directions
Mix together the brownie mix according to package directions. Line a 9x13" pan with parchment paper and spray with non-stick cooking spray. Spread half the batter in the pan - it will be spread thin. Layer the candy bars on top of the batter, then spread the remaining batter over the candy bars. Bake at 350 degrees, for about 30 minutes, or however long the directions say to bake a pan this size. Cool and cut into bars.
I've also seen this recipe made in a 9x9" square pan, so it all just depends on how thick you want the bars. If made in a 9x9" square pan, obviously you will need to bake the brownies longer, but just follow the package directions. You may only need two of the candy bars, instead of the three listed above.
Note
You can use plain milk chocolate bars if you don't want the toffee and almonds, or use any flavor of chocolate bar you prefer.