Start crushing the mint Oreo cookies until they’re fine crumbs — a food processor works best here, but a zip-top bag and rolling pin can do in a pinch.
Mix the crumbs with melted butter until everything’s soaked and combined. Press that firmly into the bottom of a 9x13 dish to get a solid crust layer that holds up.
Beat the cream cheese with powdered sugar until smooth and creamy. Fold in half the whipped topping, peppermint extract, and the green gel color until it's all a pretty pale green color.
Spread that cream cheese layer over your packed Oreo crust evenly so it covers all sides nice.
Whisk your chocolate pudding mix with the cold milk for about 2 minutes till it thickens up — don’t buy cook and serve, it won’t work for this. Then fold in the remaining whipped topping gently to keep it smooth.
Spread the chocolate layer over the green layer gently. Then pop the whole dish in the fridge for at least 4 hours so it firms up nicely before serving.
Notes
Cover the dish tightly with plastic wrap to keep fridge smells out and freshness in. You can store it in an airtight container if you slice it up beforehand.