Preheat the oven to 350 degrees F. Grease flour 2 (8-inch or 9-inch round) cake pans. I used non-stick cooking spray and dusted the pans with cocoa powder.
In a large mixing bowl, sift together flour, baking soda, and salt and set aside.
In a second mixing bowl, with an electric mixer, cream butter and sugar together until light and fluffy. Add eggs one at a time and beat vigorously until each is incorporated. Mix in vanilla.
In a separate bowl, make a paste of the cocoa powder and the food coloring. Blend into butter mixture.
Alternating in 2 batches each, add dry ingredients and buttermilk to the butter mixture. In the last batch of buttermilk, mix in the vinegar before adding to the batter. Mix until blended.
Divide batter among the 2 pans and bake for about 30 minutes until toothpick inserted comes out clean and top springs back when touched. Remove from oven and allow to cool for 10 minutes in pan.
Remove the cakes from the oven and run a knife around the edges to loosen them from the sides of the pans. One at a time, invert the cakes onto a plate and then re-invert them onto a cooling rack, rounded-sides up. Let cool completely. With a serrated knife, cut each layer in half.
Make the frosting: In a stand mixer with the paddle attachment, combine the cream cheese and butter and mix to combine about 2-3 minutes. Add in the powdered sugar one cup at a time with the mixer stopped and mixing on low after each addition until combined. Add in the vanilla and the cooled white chocolate.Increase the speed to high and mix until fluffy about 5 minutes.
Frost the cake. Place 1 layer, rounded-side down, in the middle of a rotating cake stand. Using a palette knife or offset spatula spread some of the cream cheese frosting over the top of the cake. (Spread enough frosting to make a 1/4 to 1/2-inch layer.) Carefully set another layer on top, rounded-side down, and repeat. Top with the remaining layer and cover the entire cake with the remaining frosting.
Make the chocolate covered pretzels: Melt the candy melts in the microwave. I used dipping containers, but any tall container will do. Melt the candy melts in 30-second intervals at 50% power. Stir in between each interval. Once melted, dip each pretzel rod into the chocolate, and then tap the end of the pretzel over the chocolate to allow the excess to drip off. Place on a parchment paper lined cookie sheet. Cover each pretzel immediately with sprinkles, before the chocolate cools and hardens. Place each pretzel around the cake. (I cut the ends off of the pretzels so they were about an inch taller than the cake).
Make the white chocolate curls by melting the white chocolate and vegetable shortening in a microwave safe bowl in 30-second intervals until melted. Then spread the white chocolate onto a cookie sheet using a spatula so it is a thin sheet. Place in the freezer for about 10 minutes until it hardens. Then using a small metal spatula scrape the white chocolate into curls. Top the cake with white chocolate curls.