Begin by crushing 24 chocolate sandwich cookies in a food processor until they resemble fine crumbs. Melt 4 tablespoons of unsalted butter and combine it with the cookie crumbs in a bowl. Press this mixture firmly into the bottom of a 9x13-inch dish to form a sturdy crust. For a firmer base, chill the crust in the refrigerator for about 15 minutes while you prepare the filling.

In a large mixing bowl, beat 8 ounces of softened cream cheese and 4 tablespoons of room temperature butter together using an electric mixer on medium speed. Gradually add in 1 cup of sifted powdered sugar while continuing to beat until the mixture is smooth and fluffy, about 2-3 minutes.

In a separate bowl, combine 1 package of instant vanilla pudding mix with 2 cups of cold milk. Whisk vigorously for about 2 minutes until the mixture thickens significantly.

Gently fold the prepared pudding into the cream cheese mixture until well combined. Next, add in half of a 12-ounce container of thawed whipped topping and fold it in carefully.

Spread this creamy filling over your chilled cookie crust, creating an even layer. Spread the remaining whipped topping over the filling, sprinkle the reserved cookie crumbs over the top, followed by a generous amount of pastel-colored candy-coated chocolates.

Cover the dish with plastic wrap and refrigerate for at least 2 hours, or overnight for the best flavor and texture. Once chilled, slice the casserole into 12 squares and serve it cold.