Make the Pumpkin Spice Cake:
- Pre-heat oven to 350 degrees. Grease and flour two 8-inch cake pans and set aside.
- Sift together the flour, baking powder and pumpkin pie spice. Set aside.
- Using an electric mixer, beat the butter until creamy. Add in the oil, sugar, brown sugar and mix until combined.
- Add in the eggs, one at a time, and mix until combined.
- In two batches, stir in the dry ingredients.
- Fold in the pumpkin puree.
- Divide the batter between the two prepared pans and bake for about 25 to 28 minutes, or until a toothpick inserted into the center of the cakes comes out clean. Cool on a wire rack for 15 minutes before removing the cakes from their pans.
Make the Coffee Soak:
- Combine all of the ingredients in a saucepan and place over medium-high heat. Bring the minute to a boil, then reduce the heat to a simmer.
- Simmer for about 10 minutes or until the syrup thickens slightly. Remove from heat and let cool slightly before using.
Make the Frosting:
- Place the flour, salt, and milk in a medium saucepan. Whisk until combined and there are no lumps from the flour.
- Stirring with a wooden spoon, heat over medium-high until the mixture begins to thicken and large bubbles begin to break on the surface. The mixture will look thick and pasty when done. Remove from the heat and transfer the flour mixture to heat-safe container. Press a piece of plastic wrap directly on the surface of the mixture and refrigerate until completely cool (about 30 to 45 minutes).
- Once the flour mixture has cooled, beat together the butter and sugar until soft and creamy. Add in the flour mixture and continue to mix together on medium-high until the frosting is light, fluffy, and almost white in color.
- Add in the vanilla extract and cinnamon. Mix until combined.
- Fold in the softened mascarpone until incorporated. Make sure that the mascarpone has softened and that you do no over-mix it.
Assemble the Cake:
- Once the cake has cooled, generously brush on the coffee syrup.
- Fill a pastry bag fitted with an open star tip with the frosting and pipe stars on one of the layers of cake. Place the second layer of cake on top and repeat.
- Dust the top of the cake with cocoa powder or a generous handful of chocolate shavings.
- Alternatively, fill and the cake with an off-set spatula and frost is as you wish.