Preheat your oven to 350 degrees. Lightly grease a 9" pie plate with cooking spray and set aside.
In a medium bowl, stir together the finely ground shortbread cookies and the melted butter until the mixture comes together and is completely moistened. I like to use my food processor for this, but you can do it by hand as well.
Press the mixture into the bottom and sides of your pre-greased pie dish. Bake for 12 minutes. Remove from the oven and let cool completely.
Now for the pie filling! In the bowl of a stand mixer (or a large bowl and a hand mixer), lightly mix the dry ingredients together. Keep your mixture on low the whole time so that you don't incorporate too much air. If you do, you will lose the gooey-ness of having a crack pie. Add the melted butter gradually until moist. Add in the heavy cream and the vanilla, beating again slowly to combine.
Now, add the egg yolks - gently mixing in. Do not over mix! Gently fold in the chopped Christmas Tree Cakes. Pour the filling into the prepared crust.
Bake at 350 for 17 minutes exactly. Open the oven door, just to where it's ajar, and reduce the oven temperature to 325 degrees. Bake for an additional 15 minutes. The center should be a little jiggly but will be golden brown. Close the oven door, turn off the oven, and let the pie sit in the oven for about 15 minutes. Then remove from the oven and let it cool the rest of the way on the counter. The center of this pie should be somewhat gooey - and that's ok. That's exactly what is supposed to happen with a 'crack' pie!
Decorate with red and green writing frosting, similar to the design on a Christmas tree cake - if desired. Cool completely before slicing. You can refrigerate it to hurry this process along.
