1. Prepare three 8 inch cake pans with parchment paper circles in the bottom and grease the sides. Preheat oven to 350°F (176°C).
4. Combine the flour, baking powder, spices and salt in a medium sized bowl and set aside.
5. Add the butter, brown sugar and vegetable oil to a large mixer bowl and beat together until light in color and fluffy, about 3-4 minutes. Do not skimp on the creaming time.
6. Add the vanilla extract and two eggs and mix until well combined and smooth.
7. Add the other two eggs and mix until well combined and smooth. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
8. Add half of the dry ingredients to the batter and mix until mostly combined.
9. Add the milk and mix until well combined.
10. Add the remaining dry ingredients and mix until well combined and smooth. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated. Do not over mix the batter.
11. Divide the batter evenly between the cakes pans and bake for 28-30 minutes, or until a toothpick comes out with a few crumbs.
12. Remove the cakes from the oven and allow to cool for about 2-3 minutes, then remove to cooling racks to cool completely.
13. When the cakes are ready and cooled, make the frosting. Place the butter in a large mixer bowl and beat until smooth.
14. Add about half of the powdered sugar and mix until well combined and smooth.
15. Add the mascarpone cheese and mix until well combined and smooth.
16. Add the salt, spices, vanilla extract and pumpkin puree and mix until well combined and smooth.
17. Add the remainder of the powdered sugar and mix until well combined and smooth.
18. To put the cake together, remove the domes from the tops of the cakes. To do this, I use a long serrated knife.
19. Place the first layer of cake on a cake plate or cardboard cake circle and top with about 3/4 cup of frosting. Spread the frosting into an even layer.
20. Add the second layer of cake and another layer of frosting.
21. Add the final layer of cake to the top, then frost the outside of the cake. Feel free to refer to my tutorial for frosting a smooth cake. Refrigerate the cake for a bit so that the frosting can firm up, if needed.
22. To make the orange ganache, add the candy melts to a medium sized bowl.
23. Heat the heavy whipping cream until it begins to boil, then pour it over the candy melts. Allow to sit for 1-2 minutes, then whisk until smooth.
24. Drizzle the orange ganache around the outer edge of the cake and fill in the top of the cake. I like to use a squeeze bottle, but you could also use a piping bag and piping tip.
25. Pipe the remaining frosting around the outside edge of the top of the cake, then add sprinkles. I used the Wilton 2D piping tip.
26. Refrigerate the cake until ready to serve and serve at room temperature. Cake is best when stored well covered and eaten within 2-3 days.