Begin by crushing the Oreo cookies into fine crumbs using a food processor or by placing them in a zip-top bag and smashing them with a rolling pin. Set aside ½ cup of the crumbs for topping later. Firmly press the remaining crumbs into the bottom of a 9x13 inch dish to establish a solid crust base.

In a large mixing bowl, use an electric mixer to beat together the softened cream cheese and unsalted butter until smooth and creamy, about 2-3 minutes. Gradually add the powdered sugar and mix until fully incorporated. Then, gently fold in the thawed whipped topping until fluffy to create a light and airy filling for your Easter Dirt Cake Casserole.

In a separate bowl, whisk the instant vanilla pudding mix with 2 cups of cold milk until the mixture thickens, which should take about 2 minutes. Allow it to sit for an additional 5 minutes to firm up. Then, carefully fold the thickened pudding mixture into the cream cheese mixture until everything is well combined and has a uniform texture.

Spread the creamy filling evenly over the prepared Oreo crust in the dish, smoothing it out with a spatula. Sprinkle the reserved cookie crumbs, mini Oreo cookies, and pastel candy-coated chocolates on top, creating a lively decorative layer that mirrors the colors of spring.

Cover the dish with plastic wrap or a lid and refrigerate the assembled casserole for at least 2 hours, allowing the layers to set properly and the flavors to meld.