Yellow Cake with Sour Cream Chocolate Frosting

The cake I made for Katie's birthday yesterday just might be the very best tasting cake I've ever made.  It was a classic yellow birthday cake, festively frosted in chocolate and decorated with colorful sprinkles.  The candles around the edge just invited "Happy Birthday" which Henry started singing before everyone was ready (he's four) and he blew out the candles before his mom, aka the birthday girl, or little brother Pete ever had a chance!  We re-lit one candle for Pete, since he'd been practicing blowing out candles all day, even at pictures of birthday cakes on my phone (he's two). 

So, the 2-layer yellow cake, in 8-inch rounds, was just sitting there and I was wondering just exactly what frosting would go best.  You can go in so many directions with a yellow cake.  I searched some trusted sites on the computer to find a sour-cream chocolate frosting recipe, and I found a few and adapted them to come up with my own.  First of all, a standard frosting recipe for an 8-inch round cake does NOT make enough for my needs.  I'm all into deep swirls and abundant garnishes, and so almost always double a frosting recipe in order to have more than enough (never a problem to have too much frosting, is it?). 

Katie's birthday!

Here's my recipe, inspired by many but enough my own to claim it:

YELLOW PARTY CAKE
oven - 350 degrees F
Spray and line 8- or 9-inch round cake pans with parchment paper.  Spray parchment paper.

1 cup soft, unsalted butter (room temperature)
1 1/4 cups granulated sugar
3 large eggs plus 2 extra egg yolks, also at room temperature
2 tsp. vanilla extract. 
1 cup buttermilk (or regular milk "soured" with 1 tbsp. vinegar. let sit 5 minutes)
3 cups all-purpose flour
1 tablespoon plus 1/2 tsp. baking powder
1/2 tsp. salt
few drops yellow food coloring (if desired)

Cream butter until light and fluffy.  Add sugar and cream for a long time, about 5 minutes.  Scrape bowl a few times.  Add eggs and then egg yolks, one at a time, and beat well after each addition.  Add vanilla and a few drops of yellow food coloring (optional).

In separate bowl, combine flour, baking powder, and salt.  Add alternately with the buttermilk.  Mix well until all dry particles are incorporated.

Divide batter between prepared pans but don't fill beyond 3/4 full.  If you have extra batter, make a few cupcakes after the layers come out of the oven (20 minutes for cupcakes).

Bake layers for 30-35 minutes OR (important) until cake tests done when toothpick is inserted or it bounces back when lightly pressed in the center.

Cool on wire rack for 15 minutes.  Turn out of pans and continue to cool completely on wire rack.  Cool cake for a good few hours or overnight to be sure it's settled and ready to frost.  (If you frost a cake too soon after baking, it's too tender and may break.)

Peel parchment paper off layers before frosting.

SOUR CREAM CHOCOLATE FROSTING
inspired by a recipe from allrecipes.com

6 oz. chocolate chips (semi/dark/milk - whatever you prefer) melted with 1/2 cup butter and 6 tablespoons cocoa (I used Ghiradelli). 
Cool until it reaches room temperature but don't let it solidify.  Transfer chocolate mixture to large mixing bowl.
To this, add 1 cup sour cream, 2 tsps. vanilla extract, and a dash of salt.  Combine thoroughly.  Slowly beat in enough confectioners sugar until it looks just right.  I used 5-6 cups.  I didn't sift it, but that wouldn't hurt.  Mine incorporated just fine, no lumps.

Makes more frosting than you'll need.  :)