To Make the Eggnog Cake: Preheat oven to 350F. Butter two 8” cake pans then line the bottoms with parchment paper. Set aside.
In a large bowl, combine the flour, baking powder, salt, nutmeg, and cinnamon. Mix well.
In the bowl of a stand mixer fitted with the whisk attachment, combine the butter, olive oil, granulated cane sugar, and brown sugar. Beat for 2 minutes, until light and fluffy.
While beating on LOW speed, add the eggs one at a time. Fold in the vanilla extract.
Add half of the flour mixture and half of the Holiday Nog. Mix JUST until incorporated.
Add the remaining flour mixture and Holiday Nog to once again mix JUST until combined. Try not to over mix the batter.
Divide the cake batter between the prepared cake pans, then smooth out the tops with the back of a spoon.
Bake for 25-30 minutes, until the centers are set and a toothpick inserted into the center comes out clean. Let cool for at least 10 minutes before transferring to a wire rack to cool completely.
To Make the Gingerbread Brittle: Prep all the ingredients, as well as a large baking pan lined with parchment paper.
In a large saucepan, combine the sugar, honey, water, and salt. Mix until the sugar is dissolved.
Using a candy thermometer, bring the mixture to 300F. Reduce heat to a simmer, then work quickly to stir in the butter, chopped pecans, and chopped candied ginger.
Stir in the baking soda, then immediately pour onto the prepared sheet pan. Spread out to about ¼” thick. Let cool for 15-20 minutes, until hardened.
Place in a resealable bag to break up into fine pieces. Set aside. If prepping in advance, store in a brown paper bag or airtight container away from direct heat and sunlight to preserve its crunch.
To Make the Holiday Nog Cream Cheese Buttercream: In the bowl of a stand mixer fitted with the whisk attachment, combine the softened butter and cream cheese. Beat for 2-3 minutes, until smooth.
Add the vanilla, nutmeg, and two cups of powdered sugar. Beat for 2 minutes.
Continue adding another cup of powdered sugar, beating for 1 minute in between, until a light and airy buttercream. Add the Holiday Nog to help loosen up the frosting.
To Assemble the Cake: Slice the cooled cake layers in half. Layer each cake with a generous amount of the buttercream, followed by the crumbled gingerbread brittle. Once you’ve add the final cake layer, use an offset spatula to frost a crumb coat. Place in the fridge for 15 minutes, then frost the cake with remaining buttercream as desired!