Using the microwave, melt 5 tbsp of unsalted butter in a large bowl. Add the cookie crumbs to the bowl and mix together. Dump the mixture into a 13"x9" baking dish and press it down evenly across the pan to form the crust. Bake for 6 minutes until heated through and set/dry. Let cool.

In a small bowl, melt 4 oz of semi-sweet chocolate chips with 4 tbsp unsalted butter in the microwave at 30 second intervals, stirring between each interval, until fully melted and combined. Let cool.

In a large bowl, microwave 8 oz cream cheese at 15 second intervals, stirring between each interval, until very soft. With a hand mixer or stand mixer, beat the cream cheese until smooth (no lumps!), about 1 minute. Add in 1.5 cups of powdered sugar. Beat until combined. Pour in the cooled chocolate/butter mixture and 1/4 cup cocoa powder and beat until combined. Set aside.

With a hand mixer or stand mixer (using the wire whisk attachment) and a large bowl, whip 2.5 cups of heavy cream until frothy and beginning to thicken. Add in 1/3 cup of powdered sugar and 1/2 tsp of vanilla extract. Continue beating until soft peaks form and then beat a bit more until the whipped cream is just beginning to form stiff peaks. Don't overbeat.

Roughly divide the whipped cream in half and add half to the chocolate layer mixture we set aside earlier (no need to be too precise!) Fold the cream in gently, taking care to avoid removing too much air. When no streaks remain, pour the chocolate filling over the (cooled) cookie crust. Spread evenly. NOTE: if you want to pipe the whipped cream layer onto your pie, you should reserve a bit more than half the amount of cream to ensure you will have enough for piping.

Finally, top the chocolate layer with the remaining whipped cream. You can choose to pipe it from a pastry bag if you are feeling fancy. Otherwise just spread it with a spoon.