Place the chocolate sandwich cookies into a food processor and pulse until they become fine crumbs. If you don't have a processor, place them in a sturdy zip-top bag and crush them with a rolling pin. Leave a few slightly larger crumbs for extra crunch.
Whisk together the instant chocolate pudding mix and cold milk until completely smooth. Let the mixture sit for about 5 to 7 minutes so it thickens into a creamy pudding consistency.
In another bowl, whip the heavy cream until medium peaks form. This creates a light and airy texture that makes the dessert extra creamy.
Gently fold the whipped cream into the thickened pudding using a spatula. Mix carefully so the filling stays fluffy and smooth without losing volume.
Stir about three-quarters of the crushed cookie crumbs into the pudding mixture. This creates the signature dirt appearance while adding a delicious chocolate cookie crunch.
Divide the pudding mixture evenly among eight serving cups or small jars. Smooth the tops with the back of a spoon for an even finish.
Sprinkle the remaining cookie crumbs over each cup to resemble fresh soil. Add three gummy worms to each serving and decorate with chocolate rocks if desired.
Refrigerate the cups until you're ready to serve. They taste wonderful chilled, and the flavors blend together beautifully after resting for a little while.