Start by crushing the Oreo cookies into fine crumbs. Reserve ½ cup of the crumbs for later use. In a 9x13 inch dish, mix the remaining crumbs with softened unsalted butter until well combined. Press into the bottom of the dish.

In a large mixing bowl, use a hand mixer to beat the softened cream cheese, unsalted butter, and powdered sugar together until smooth and creamy.

In a separate bowl, whisk together the instant vanilla pudding mix and cold milk until it thickens. Carefully fold the pudding mixture into the cream cheese mixture.

Spread the creamy filling evenly over the prepared cookie crust. Sprinkle the reserved Oreo crumbs on top, and add mini Oreo cookies and pastel candy-coated chocolates.

Cover the casserole with plastic wrap and refrigerate for at least 2 hours to let it set properly.