This was a revelation when I made it. The custard texture is unusually light, practically melting in your mouth, and the depth of flavor that comes from the spices, the egg nog, and the pumpkin is spectacular.
Arrange oven racks so there is one in the lower third for your pie. Preheat oven to 425 degrees.
Line a 9 inch pie plate with the crust, turning top part under and pressing to form a decorative edge, if you like . Keep in the fridge until your filling is ready.
Mix all remaining ingredients (except the whipped cream and cinnamon sugar!) in a large bowl using a wire whisk. Pour into prepared crust.
Cover the edges of the pie with tin foil, or a crust protector if you have one, to prevent them from getting too brown while the custard bakes.
Bake on that lower oven rack at 425 degrees for 15 min. Turn heat down to 350 degrees and continue baking for 45-55 minutes, or until the center is set and a sharp knife comes out clean. Cool on wire rack for 2 hours.
If you have time, refrigerate for several more hours or overnight. Take out 1 hour before serving to warm pie to room temperature. Slice and garnish with fresh whipped cream, dusted with a bit of cinnamon sugar.