Cranberry White Chocolate Champagne Cake

Preheat oven to 350°F. Grease three 8-inch pans and line with parchment paper.
Place champagne in a small saucepan and set over medium heat. Let reduce to 1 cup (this takes around 15-20 minutes). Let cool and set aside.
In a small bowl, combine flour, baking soda, and salt. Set aside.
In a large bowl, cream together butter and sugar using an electric mixer. Beat in egg whites, vanilla, and sour cream.
Mix in 1/2 of the flour mixture. Beat in champagne and milk. Mix in remaining half of flour mixture.
Divide mixture into 3 cake pans and bake 22 minutes or until a toothpick inserted in the center comes out clean. Let cakes set in pans for 5 minutes, then remove and place on a wire rack to let cool completely.

Place chocolate chips in a small, heatproof bowl. In a separate microwavable bowl, heat heavy cream on high in the microwave until boiling. Pour over chocolate chips and cover bowl with plastic wrap. Let set for 10 minutes and then whisk mixture together until smooth.
Transfer white chocolate mixture to a larger bowl and with an electric mixer, beat on medium speed until fluffy. Beat in butter and powdered sugar, one cup at a time.

Place water and cranberries in a medium-sized saucepan. Place over medium heat and cook until cranberries burst. Stir occasionally. Remove from heat and mash with the back of a spoon or a potato masher. Place mixture into a mesh sieve, and scrape the cranberry mixture off the bottom. You should have about 1c of strained cranberry puree. This step may take a few minutes.
In a small bowl, whisk together egg yolks and whole egg, and orange liqueur.
Return cranberry mixture to saucepan and add butter, sugar, cornstarch, and salt. Cook over medium heat, stirring often, until butter is melted and incorporated.
Whisk in 1/4 cup of the cranberry mixture into the egg mixture. Return egg/cranberry mixture to saucepan and cook the entire mixture over medium heat until mixture thickens and coats a spoon. Whisk constantly. Remove from heat and place mixture in a heatproof bowl and place plastic wrap directly on mixture. Place in the refrigerator and let cool completely before using.

Pipe or spread a ring of frosting along outer edge of one cake layer. Fill the center of this ring with 1/3 of cranberry curd mixture. Place another cake layer on top and repeat this step.
Frost top and sides of cake and spread remaining 1/3 cranberry curd on top. Decorate the top as you desire. I used cranberries and rosemary sprigs, but you can also use pomegranate seeds or whatever else you prefer.