Start by crushing the Oreos in a food processor or a zip-top bag with a rolling pin until they resemble fine crumbs. In a mixing bowl, combine the crushed Oreos with the melted butter. Mix until the crumbs are evenly coated. Press this mixture firmly into the bottom of a 9x13-inch baking dish to form a solid crust.
In a large mixing bowl, beat the softened cream cheese with an electric mixer until smooth and creamy. Gradually add the powdered sugar, mixing until well combined. Pour in the milk and peppermint extract, continuing to mix until everything is incorporated. Add the green food coloring and stir until you achieve a lovely mint hue. Gently fold in the whipped topping until everything is light and fluffy.
Spread the mint filling evenly over the Oreo crust in the baking dish. Use a spatula to smooth it out evenly, ensuring every corner is filled.
In a separate mixing bowl, whisk together the cold milk and instant chocolate pudding mix until it thickens. This should take about 2 minutes. Once thickened, fold in the mini semi-sweet chocolate chips for added texture.
Pour the chocolate pudding layer over the mint filling, using a spatula to spread it evenly across the surface.
Spread the whipped topping evenly over the chocolate layer, smoothing it out for a beautiful finish.
Sprinkle the chopped mint chocolate chunks over the top for an extra touch of flavor and a pop of color.
Cover the dish with plastic wrap and refrigerate for at least 4 hours, or overnight if possible. This allows the layers to set and the flavors to meld beautifully. Once chilled, slice into squares and serve, enjoying the delightful combination of chocolate and mint!