Don't even read on if you're not a chocolate lover.
Use your favorite basic brownie recipe. Bake and cool. Frost by spreading with a thin layer of peanut butter. Top with chopped Reeces peanut butter cups (Walmart/Sam's brand are great, too) Add chopped peanuts if you want more crunch.
There. If that's not enough chocolate for you, I don't know what is.
The other idea is: Frost with caramel ice cream topping. Top with chopped macadamia nuts and chocolate chips. Oh, yeah.