Prepare a 9x13 inch baking dish by lightly spraying with non-stick cooking spray or lining with parchment paper.

Combine crushed Oreo cookies with melted butter, stirring until all crumbs are evenly moistened.

Press Oreo mixture firmly and evenly into bottom of prepared baking dish. Refrigerate while preparing next layer.

Beat softened cream cheese and butter together using electric mixer on medium speed until smooth and creamy, about 2-3 minutes.

Add powdered sugar, peppermint extract, and green food coloring to cream cheese mixture. Beat until fully combined and fluffy.

Gently fold in 8 oz of thawed Cool Whip into cream cheese mixture using a spatula. Mix until just combined and color is uniform.

Spread mint cream cheese mixture evenly over chilled Oreo crust. Return to refrigerator for 15-20 minutes to set.

Whisk together instant chocolate pudding mix and cold milk for about 2 minutes until mixture thickens to pudding consistency.

Carefully spread chocolate pudding over chilled mint layer, creating an even layer. Refrigerate for another 15-20 minutes.

Spread remaining 8 oz of Cool Whip over chocolate pudding layer, creating fluffy peaks and swirls.

Sprinkle crushed Oreo cookies over whipped cream topping, covering entire surface evenly.

Cover tightly with plastic wrap and refrigerate for at least 4 hours or overnight. Before serving, garnish with fresh mint leaves and drizzle with chocolate syrup if desired.