you'll simple bake your brownies as the box suggests, chop them up into bite-sized pieces, and select your flavorful mix-ins. I particularly like a "chocolate covered strawberry" styled brownie ...
It's definitely possible to add any of these forms of fruit into your boxed brownie mix, but each has a different method of preparation. If using fresh or frozen fruit, it's ideal to first roll or ...
Although I think boxed brownie mixes are pretty close ... chocolate to toss into the batter. Even if your mix already has chocolate chips, add in the chopped chocolate anyways.