Crush the Oreos to fine crumbs using a food processor. Set aside ½ cup / 75g for later in an airtight container and pour the rest into a medium mixing bowl.
In a heatproof bowl, melt the butter (in the microwave for 30secs) and stir into the crushed Oreos.
Press half of the Oreo butter mixture into the base of your glass dish. Refrigerate this and leave the other half on the side at room temperature.
In a medium bowl, stir together the milk and pudding mix until smooth, then refrigerate.
Using a stand mixer or a hand mixer in a large mixing bowl, beat the cream cheese and icing sugar until fully combined.
In a separate bowl, whip the cream using a hand mixer or stand mixer until stiff peaks form.
Fold the whipped cream into the cream cheese mixture then gently stir in the instant pudding until smooth.
Pour half of the cream mix into your dish, smoothing gently, then evenly layer on the other half of the Oreo-butter mixture.
Smooth the remaining cream mixture on top and refrigerate for at least 3hrs or overnight before sprinkling over the ½ cup / 75g crushed Oreos and decorating.