Preheat oven to 325 degrees
Start by preparing the boxed brownies according to the directions on the package. I use the Duncan Hines Chewy Fudge Brownie mix that called for 2/3 c oil, 2 eggs and 3 T water to be combined with the brownie mix. Use mixer to combine. Once well mixed, set batter aside.
Crush about 30 Oreo sandwich cookies. You will use some in the brownie batter, and some as the "cookie dirt" topping. Place cookies in a Ziplock bag (be sure to seal it), and use the bottom of a heavy drinking glass to smash the cookies into smaller, bits.
Add half of the crushed cookies (approx 1.5 cup) to your brownie batter and stir to combine.
Spray your pan with cooking spray. I like to use a 9 x 13 sided pan as it makes a nice, long space to decorate as a graveyard.
Cook your brownies according to the directions on box. I use a metal pan, so I cook mine at 325 degrees for 24-27 mins. Note: if using a glass pan, cooking time may increase a few mins, so be sure to follow directions accordingly.
You can tell if brownies are fully cooked by inserting a toothpick into the center of them. If the toothpick comes out clean, then the brownies are done. If the toothpick comes out with some batter on it, pop your pan back into oven for a few more mins, and repeat toothpick test. Let brownies cool before you frost.
Spread chocolate frosting evenly across top of cooled brownies, I use about 3/4 of the can of frosting. Using a spoon, sprinkle the remining crushed Oreo cookies over the top of the frosting layer.
Place your gravestones into the cookie layer wherever you like. I like to use an odd number as it's more interesting to the human eye. Tip: if the gravestones sit up too high, snip off the bottom of the cake topper to make them shorter.
Grab your gummy worms and place them in between the tombstones. Vary the direction of them for more interest.
I like to serve these brownies in the pan so my guests can see the whole graveyard scene. I let them serve themselves and cut off as much or as little as they'd like.