Step 1: Begin by preparing your Oreo “dirt.” Place about 36-40 Oreo cookies into a food processor. Pulse until they resemble fine crumbs, with a few slightly larger pieces for texture. Set aside.
Step 2: In a large mixing bowl, beat the softened cream cheese and softened unsalted butter with an electric mixer until light and fluffy, about 2-3 minutes.
Step 3: Gradually add the powdered sugar to the cream cheese mixture, beating until well combined and smooth. Scrape down the sides of the bowl as needed.
Step 4: In a separate bowl, whisk together the cold milk and instant vanilla pudding mix until thickened, about 2 minutes. Let it sit for a minute or two to thicken further.
Step 5: Gently fold the prepared pudding mixture into the cream cheese mixture until just combined. Then, fold in the thawed whipped topping until no streaks remain.
Step 6: To assemble, spread about one-third of the crushed Oreo crumbs evenly on the bottom of a 9×13 inch pan or large trifle dish.
Step 7: Carefully spoon half of the creamy pudding mixture over the Oreo layer, spreading it gently to the edges.
Step 8: Sprinkle another third of the Oreo crumbs over the creamy layer. Repeat with the remaining creamy mixture, then top generously with the remaining Oreo crumbs.
Step 9: Arrange gummy worms or other candy decorations on top of the “dirt” layer, making them look like they’re crawling out of the dirt.
Step 10: Cover the pan loosely with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, to allow the flavors to meld and the cake to set completely.