Preheat the oven to 350°. Line the bottoms of 3-9” cake pans with parchment paper and lightly spray with baking spray. Set aside.
In a large mixing bowl combine flour, cake flour, baking powder, baking soda and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment mix together sugar and butter. Beat on medium speed until smooth. Add in the vegetable oil and mix to combine.
Add in the eggs and mix for 30 seconds, then add in the buttermilk, sour cream, vanilla and optional butter flavoring. Mix on medium speed until incorporated.
Add in the flour mixture and mix until just combined.
Evenly divide the batter between the 3 prepared cake pans.
Place the cake pans into the preheated oven on the center rack. Bake for 45 minutes, until a toothpick inserted into the center of the cakes comes out clean or with a few moist crumbs.
Once baked, remove from the oven and place onto a wire cooling rack to let them completely cool.
White Chocolate Snowflakes
To make the snowflakes, place the white chocolate chips into a heat safe bowl. Microwave for 30 seconds at a time, stopping in between each segment to stir. This will prevent the chocolate from burning. Once the white chocolate chips are completely melted and smooth, set aside to cool down slightly. Once slightly cooled, transfer the melted chocolate into a plastic baggie.
Place a large piece of parchment paper onto the counter. Snip the edge of the baggie and pipe snowflakes onto the paper. You will want to go over each line/stick twice with the chocolate to make sure they are sturdy enough to stand up once they are set.
Space the snowflakes out about 5” apart, making various sizes. Sprinkle sugar crystals over top before the chocolate sets.
To Make the Frosting
In the bowl of a stand mixer fitted with paddle attachment combine powdered sugar, butter, vanilla and salt. Mix on low speed until combined.
Once combined, turn the mixer speed up to medium-high and beat for 3 minutes, until white and fluffy. Remove about 1⁄3 of the frosting from the mixing bowl and place it into a separate bowl. This frosting will remain white.
To the remaining frosting in the stand mixer bowl, add in drops of blue food coloring until the desired color is reached. Mix for 1 additional minute, until the color is incorporated throughout the frosting.
Assembly
Once the cakes have completely cooled and the snowflakes have set, carefully remove the cakes from the pans. Place the 1st cake onto a cake stand or plate.
Add about 1 cup of blue frosting on top, then evenly spread out using an icing spatula.
Place the 2nd cake on top and repeat the frosting process, except using the white frosting this time.
Top with the 3rd cake layer, then frost the top and upper half of the cake with the white frosting. Use an icing spatula to get a smooth finish.
Frost the bottom half of the cake with the blue frosting blending in with the white on the upper half of the cake. Blend the colors together by pulling the icing spatula around the cake multiple times until smooth and blended. You will need to scrape off the excess frosting from the icing spatula in between rounds and smoothing.
Once the cake is frosted, sprinkle sugar crystals on top. Gently place the snowflakes around the sides of the cake.
In order to have snowflakes on top, you will need to make small slits in the top of the cake with a knife, then you will be able to slide a point of the snowflake into the cake to keep it standing. Arrange the snowflakes on top of the cake as desired.
Notes
Once the flour mixture is added into the recipe, make sure to only mix until just combined. Overmixing can cause the gluten to overdevelop, resulting in a crumbly cake.
Optionally add a small amount of shortening to the white chocolate before you melt it. This will help with the smoothness of the chocolate once it is melted.
When mixing up the frosting, it is important to stop the mixer and scrape down the sides of the mixing bowl with a rubber spatula. This will ensure a smooth, lump free frosting.
Cake may be stored in an airtight container for up to 3 days at room temperature.