The top 8-inch tier is white sour cream cake frosted in vanilla buttercream tinted pink. I used the piping bag liner trick to decorate this cake. The bottom 10-inch layer is chocolate sour cream cake frosted in double chocolate buttercream.
Double Chocolate Buttercream Frosting
1/2 cup unsalted butter, softened, but not melted
1/2 cup chocolate chips, melted
2 teaspoons vanilla extract
1/4 cup cocoa powder
5 cups powdered sugar
1/2 cup heavy cream
In the bowl of a stand mixer, beat butter until light and fluffy. Add melted chocolate, vanilla extract, and cocoa powder. Mix until blended. Add powdered sugar alternately with the cream, mixing after each addition. Scrape sides of bowl and beat an additional minute. Add a little more powdered sugar if needed, or a little more heavy cream if frosting is too stiff.