Prepare a standard store-bought brownie mix as directed on the package except mix in one sleeve of crushed mint chocolate covered cookies* and 1 cup of chopped nuts into the batter. Bake as directed on the brownie package.

*For the crushed mint cookies, I've found two great options.  During girl scout season, I use their chocolate mint cookies.  The rest of the year, I use the chocolate-covered Oreos with mint filling.  In either case, I just place the cookies in a large plastic bag and then use my rolling pin to crush them prior to adding them to the brownie batter.

Another option is to stir in regular crushed Oreo cookies and bake as directed on the brownie box (I reserve about 3/4 crushed cookies for on top the brownies).  After the brownies have cooled, sprinkle them with the reserved crushed Oreos.  Then melt 1 cup of white baking chips in the microwave inside a small ziploc bag (takes maybe 25 seconds to melt). Cut a tiny hole in the corner of the bag and squeeze to create drizzles over the top of the brownies.  These Cookies n' Cream brownies are shown in the photo.

Find many other ways to spice up your brownies here!