How to Make It
Preheat oven to 350°F with rack in lowest position. On a lightly floured surface, roll dough into a circle about 14 inches in diameter and place in a 9-inch pie plate. Using your fingers, fold under any overhang so crust just covers the lip of the plate. Crimp the edge as desired and freeze 15 minutes.
Line pie shell with a piece of parchment paper and fill with pie weights, dried beans, or rice. Bake until edges look dry and golden, 25 to 30 minutes.
Remove parchment paper and weights and immediately scatter chocolate chips over bottom of crust. Let sit 1 minute. Using the back of a spoon or offset spatula, spread chocolate evenly over bottom and up the sides of the pie shell.
Whisk together pumpkin, eggs, sour cream, milk, brown sugar, vanilla, cinnamon, ginger, salt, and cloves until evenly combined. Pour into pie shell and return pie to lowest rack. Bake 20 minutes.
Meanwhile, make the crumble. Combine flour, brown sugar, cocoa powder, cinnamon and salt in a small bowl. Add butter and use your fingers to knead until clumpy. Place bowl in the refrigerator.
Sprinkle crumble on top of pie and continue to bake until just set, 30 to 40 minutes more. Let cool to room temperature then refrigerate overnight.