Preheat oven to 350 degrees F. Grease two round 8-inch cake pans. Place round pieces of parchment paper in the bottom of each cake pan and grease the parchment paper. Flour the bottom and sides of the cake pans by tapping a spoonful of flour around to coat. Discard any remaining flour.
In a measuring cup, whisk together the egg whites, ¼ cup of milk, and the vanilla. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, combine the dry ingredients on low speed for 30 seconds.
Add in the butter and the remaining ½ cup of milk. Mix on low speed just until moistened. Increase the speed to medium and mix for 1 ½ minutes.
Scrape down the sides of the bowl. With the mixer on medium speed, add the egg mixture in 3 batches, beating for 20 seconds after each addition.
Divide the batter evenly into the cake pans using an offset spatula to level the batter. You can weigh the cake pans on a kitchen scale to ensure even layers.
Bake for 20-30 minutes or until a toothpick inserted into the center comes out clean. Be very careful not to over bake! Let cool in pans for 10 minutes. Loosen the sides of the cakes with a small knife or spatula and invert cakes onto greased wire racks. Gently re-flip the cakes so that the top of the cakes are facing up. Let cakes cool completely.
Wrap the cakes tightly until they are ready to be frosted. The cakes can be stored at room temperature for 2 days and in the refrigerator for 5 days.
For the Whipped Vanilla Frosting:
In the bowl of a stand mixer fitted with the whisk attachment, whip the butter on medium speed until pale and creamy, about 8 minutes.
With the mixer on low, add in the remaining ingredients and mix for 1 minute. Increase the speed to medium and whip until frosting is very light and fluffy, about 6 minutes.
For the Gum Paste Snowflakes (see my note at the top):
Roll out gum paste to about ⅛” thickness.
Cut out snowflakes of different sizes. Cut floral wire into varying lengths.
Very carefully insert floral wire into the snowflakes, making sure to insert far enough to provide support to the snowflake.
Lightly dip one brush into either clear alcohol or extract (it will evaporate out as it dries). Brush onto the snowflake. With the other brush, brush on the luster dust until completely covered and shimmery. (I did this whole step one snowflake at a time.)
Let snowflakes rest to dry out. Best if done at least the day or night before using.
To Assemble the Cake:
Place the bottom cake layer bottom/flat side down on a cake stand (or any dish that you will be serving it on).
Place about 1 cup of frosting on the top and spread it evenly with an offset spatula.
Gently place the 2nd cake layer top/rounded side down on top.
Place a small amount of frosting on top of the cake and create a crumb coat by spreading the frosting thinly over the top and sides with a small offset spatula. Place in the refrigerator and chill for about 30 minutes.
Remove the cake from the refrigerator. Place remaining frosting on top of the cake and spread it evenly over the top and sides. You can make the frosting textured to look like freshly fallen snow, as I did, or make it smooth.
Pour sanding sugar all over the top of the cake. Carefully tilt the cake slightly to pour sanding sugar on the sides. Rotate the cake and repeat until all sides are coated in sanding sugar.
Place the cake back in the refrigerator and chill for about 30 minutes.
Remove the cake from the refrigerator. Carefully insert snowflakes into the cake. Make sure to vary the heights so that it really looks like falling snow.
Enjoy your beautiful White Christmas Cake!
*Nicole’s Note: I suggest making the gum paste snowflakes at least one day in advance so that they are completely dry.*