Preheat oven to 350.
In 2 9" cake pans spray with cooking spray and place 2 rounds of parchment paper in bottoms, set aside.
In bowl with hand mixer cream together your brown sugar and butter until fluffy. Slowly pour in your oil.
Add your egg yolks one at a time, making sure to mix good after each addition.
In another bowl mix together your flour, baking soda, baking powder, spices and pinch of salt until combined.
Alternate adding your dry mixture and buttermilk into your butter/sugar mixture in 3 separate additions, mixing well after each.
In small bowl beat your egg whites until stiff peaks form, fold into your cake batter.
Pour batter evenly into pans and bake for about 25 minutes or until center is set.
Remove from oven and let sit for about 5 minutes then turn out onto cooling racks.
Meanwhile to make your cinnamon cream cheese filling in large bowl beat your butter until fluffy, about 2-3 minutes. Add in your cream cheese and vanilla and continue to beat for another few minutes until combined.
Add your powdered sugar 1 cup at a time until incorporated. Lastly mix in your cinnamon.
Refrigerate until ready to use.
To make your Pumpkin Buttercream in bowl add your butter and shortening and mix until smooth.
Add in your pumpkin and pumpkin pie spice and mix until incorporated.
Add in powdered sugar 1 cup at a time until blended adding in your milk or cream until desired consistency is reached.
Once cakes are cool, using a cake leveler or a serated knife, cut cakes in half, placing one layer onto a turntable.
Remove your cream cheese filling from refrigerator, top cake layer with about 1/2 cup of frosting and spread to about 1/2 away from side. Repeat with remaining layers reserving about 3/4 cup of frosting for decorating outside of cake.
Do not use to frost top layer.
Fill a large piping bag fitted with a flat cake icer tip with your pumpkin buttercream and spin your cake while piping in large bands around cake. Spread smooth with large spatula.
Add some of the frosting to the top of the cake and spread smooth with spatula.
Spin turntable around with your spatulas side at an angle smoothing out sides as you turn.
Once smooth, fill another piping bag fitted with a large star tip with the rest of your cream cheese frosting and pipe small swirls on top if desired and dab little stars around cake.
Place in freezer for about 20 minutes to harden up if desired before cutting.
NOTES
We like to freeze our cake after we add the filling to make it more solid before frosting the outside.