Preheat oven to 350 degrees. Spray 3 8-inch round cake pans with non-stick cooking spray and line the bottom of each pan with a circle of parchment paper.
Mix together the sugar oil, pumpkin, eggs and vanilla until mixed well.
Add the flour, baking soda, baking powder and spices to the same bowl. Stir to combine until just mixed but smooth. Do not overmix.
Divide batter evenly between the three cake pans and bake for 25-30 minutes, or until a toothpick inserted into the middle of the cake comes out clean.
Set cake aside to let it cool in the pans for 30 minutes to an hour, and then drag a knife along the outside of the cake to make sure it isn’t sticking to the pan at all. Turn the cake out onto a wire rack.
Level the cakes using a leveler to remove the curved top. Toss top, or use in another recipe like cake pops or cake truffles.
Meanwhile, place the white chocolate in a bowl. Heat the heavy cream in the microwave until it is very hot. Pour the heavy cream over the chocolate. Allow this to sit for 3-5 minutes. Mix the heavy cream and chocolate together until it is completely combined. The mixture will be smooth and shiny.
Add the pumpkin puree and spices. Mix well.
Place the ganache into the refrigerator to chill for about 1 hour. It will firm up as it gets colder. When cooled all the way, whip the chocolate ganache with a hand-held mixer. The mixture will becoming fluffier and look "whipped".
To assemble the cake, start with a cake layer (top side down a cake plate). Top with 1/3 of the filling. Repeat with the next two layers. If desired, add some of the filling to a decorating bag and use a icing tip to decorate the top of the cake.
If desired, top with additional garnishes like caramel sauce, chocolate ganache, and/or pecans.
Store the cake in the refrigerator.
The calories shown are based on the cake being cut into 12 pieces, with 1 serving being 1 slice of cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information.**