Preheat oven to 300° F. Line the bottom of an 8x8 baking pan with parchment paper. In a small bowl, mix butter, sugar, vanilla, and flour until you have a thick, sticky dough.
Press into the bottom of prepared baking dish in a single thin layer and bake at 300° F for 10-15 minutes.
Mix sugar, cinnamon, salt, ginger and cloves in small bowl. Beat eggs in large bowl. Stir in pumpkin and sugar-spice mixture. Gradually stir in evaporated milk.
When shortbread layer is done, remove from the oven and pour over your pumpkin mixture. Raise the oven temperature to 325 degrees, and bake again for 25-35 minutes until top is set; you'll see a little wiggle in the middle.
Take out and allow to cool COMPLETELY. These slice up easier if you put them into the refrigerator and cool. It also helps the filling to finish setting up.
Then cut into squares and serve!