Crush the Oreos in a food processor until they're fine crumbs. No processor? A ziplock bag and a rolling pin will do.
Mix the crumbs with melted butter until combined, then press firmly into a 9x13 inch dish. Pop it in the fridge to chill while you work on the next layer.
In a bowl, beat softened cream cheese until smooth. Add 2 tablespoons of cold milk and sugar, mix until fluffy. Fold in about a third of the Cool Whip.
Spread this dreamy layer over your Oreo crust. Take a deep breath—yes, it's already smelling incredible.
In a separate bowl, whisk chocolate pudding mix with 3 1/4 cups of cold milk until thick. This takes about 2 minutes.
Spread the pudding over the cream cheese layer evenly. You might be tempted to stop and eat this as-is. Resist.
Top it with the remaining Cool Whip and a generous sprinkle of mini chocolate chips.
Let it chill in the fridge for at least 4 hours (or overnight, if you have superhuman restraint). Slice and serve cold.