Preheat oven to 350°F. Grease and flour 3 8-inch cake pans, set aside.
In a medium size bowl, combine flour, baking powder, baking soda, salt and spices (cinnamon through black pepper). Whisk together and set aside.
In the bowl of a standing mixer, or using a large bowl with a hand held mixer, add light brown sugar, vegetable oil, molasses and apple sauce. Cream together on medium speed, making sure there are no lumps left from the brown sugar. Add eggs and vanilla, mix on low speed 1 to 2 minutes until incorporated.
Working in three batches, add the dry ingredients to the wet ingredients on low speed. Mix to combine ingredients, scraping down the sides of the bowl when necessary.
Divide the cake batter evenly between the three pans. Bake at 350°F for 25 to 30 minutes until a toothpick comes out clean.
Let cake cool and prepare the frosting. Once cake is completely cool, frost each layer and top and sides of the cake. Once frosted, lightly drip the cooled ganache over the sides of the cake. Pour ganache over the top and lightly smooth. Optional: Once ganache has set, lightly sprinkle top with spices.
Cream the butter on medium-high speed until pale and fluffy. Reduce speed to low, slowly adding confectioners sugar one cup at a time.
Add eggnog one tablespoon at a time, raising speed to medium. Add ground nutmeg and beat for 2 minutes to incorporate. Reduce speed to add heavy cream without splashing, slowly increase speed medium-high to whip the cream into the frosting. Beat for 1 to 2 minutes until frosting is light and fluffy.
White Chocolate Ganache
In a small saucepan, bring heavy cream to a simmer. Pour hot cream over white chocolate chips in a heat proof bowl. Stir with a spatula until smooth. Let sit for 10-20 minutes until cool but still liquid. The warmer the chocolate ganache is, the longer your drips will be. How long you cool it is a matter of preference and patience.