Step 1

Preheat the oven to 325 degrees. Prep a 9x13 cake pan with cake goop, baking spray, or shortening + flour. Set aside.

Step 2

In a large bowl, hand-whisk together the ingredients except for the yellow cake mix. Sift the cake mix in, then gently stir to combine. Spread into the prepared baking pan and bake for 22-25 minutes. Let cool completely.

Step 3

For slicing the cake in half, flip the cake out onto the counter on a sheet of parchment paper. Use a cake leveler to carefully slice the cake in half. Carefully slide the thin cutting board under the top layer and lift it off. Add the cake layer back into the 9x13 pan. Spread on the whipped cream filling from the next step, then flip or slide the other cake layer onto the filling layer.

Step 4

Chill a metal bowl & whisk in the freezer for 5 minutes. Place them onto the stand mixer, then add in the heavy cream. Starting on low speed and slowly working your way up to high speed over the span of 2-3 minutes, whip up the heavy cream on low for 1 minute, then medium for 1 minute, then high for 1 minute until stiff peaks form. Add in the vanilla, almond, and powdered sugar. Whip up again, then spread out onto the bottom half of the sliced cake. Add the top layer on top using the method described above.

Step 5

In a small bowl, heat up the heavy cream and white chocolate in the microwave for 30 seconds, and stir. Repeat for 10 seconds if needed, then stir until smooth. Set aside. Whip up the butter in a stand mixer with a paddle attachment until light and fluffy. Add in the salt and vanilla, then add in the white chocolate mixture (ganache). Whip up again, then add in the powdered sugar. Add in more heavy cream if needed, then turn the speed on high until the buttercream is lighter in color and texture, about 2 minutes. Beat down with a wooden spoon to remove some of the air bubbles. Frost the cake (reserving about 2 1/2 - 3 cups of the buttercream for the border), using a flat cake scraper.

Step 6

Add 2-3 drops of red gel coloring to the remaining buttercream, then pipe (using a small circle tip) a red wavy pattern like you see in these photos and on the trees. Next, fill a piping bag with the large star tip and the remaining red buttercream. Pipe a shell border around the outside of the cake. Sprinkle the green sanding sugar in the middle of the cake, then add on the festive Christmas sprinkles around the outside of the cake. Enjoy!