Mix chocolate cookie crumbs, butter and sugar together in a bowl.
Firmly press mixture onto the bottom and up sides of a deep dish, 9 1/2-inch pie dish. Make the sides thicker than the bottom to ensure a clean slice.
Bake the crust for 10 minutes then remove from the oven.
Reduce the oven temperature to 325 degrees.
In a microwave safe dish, melt the butter and chocolate together, then stir until smooth.
Mix pumpkin, chocolate, condensed milk, brown sugar, eggs, cornstarch, vanilla, salt, cinnamon, ginger, nutmeg and cloves together in a large bowl.
Whisk the chocolate/butter mixture into the pumpkin, combining completely. Pour pumpkin mixture into crust.
Bake on the centre rack in the oven until the middle of the pie is set but still a bit wobbly, around 60 minutes (start checking around 50 minutes).
Remove from the oven and cool on a pie rack,
Cool for a a couple of hours to let it set and you can also chill it overnight.
Before you serve it, melt the white chocolate in the microwave and then drizzle over the top. Let the chocolate set (around 2 minutes on a cold pie then slice and serve! (We ate the pie warm two hours later and it was delicious AND held together fine!)