Chocolate Sour Cream Cupcakes with Chocolate Buttercream Frosting

A simple tray of chocolate cupcakes is almost always appropriate, especially with a thick, rich batter:

This particular batter resembled a traditional cake batter, until the sour cream...

was swirled in and made it richer and lighter:

To complement the rich cake, I made a rich buttercream consisting of confectioners sugar sifted with cocoa:

Which was then blended with butter and vanilla before melted chocolate was added:

As I recently purchased a new pastry tube, I had lots of fun with the decorations!