Coca Cola Cake

I've almost forgotten about this yummy cake that I've baked one month ago. Anyway, the recipe is taken from Lisa Yockelson's Chocolate Chocolate.

Coca Cola Cake Recipe

Ingredients:
½ cup buttermilk
1 tsp baking soda
½ pound unsalted butter, cut into large chunks
1 cup Coca Cola
¼ cup unsweetened cocoa powder
2 cups all purpose flour
2 cups caster sugar
½ tsp salt
2 large eggs
2 tsp vanilla extract

Garnish (optional):
Unsweetened cocoa powder, for sprinkling
Chopped pistachio

The Cake

Method:
1) Preheat the oven to 400 deg F. Grease the inside of a 13 by 9 baking pan.
2) Whisk the buttermilk and baking soda together in a small bowl. In a few minutes, the buttermilk will swell.
3) Place the butter, Coca-Cola, and cocoa powder in a large saucepan, set over moderately high heat, and bring to boil.
4) In the meantime, sift the flour with the sugar and the salt into the bowl of a freestanding electric mixer fitted with the whisk attachment. Pour the hot Coca-Cola mixture over and mix on moderately low speed until thoroughly combined, about 2 to 3 minutes.
5) Blend in the eggs, vanilla extract, and buttermilk-baking soda blend. Mix well to combine. The batter will be thin.
6) Pour and scrape the batter into the prepared pan.
7) Bake the cake for 20 minutes, or until risen, set, and a toothpick inserted in the center withdraws clean. The baked cake will pull away slightly from the sides of the baking pan.
8) Let the baked cake stand in the pan on a cooling rack for 5 minutes.
9) **Frost the cake: Carefully place dollops of the frosting on top of the hot cake. Smooth over the frosting with a small offset palette knife or rubber spatula, taking care not to cut into or dislodge the top of the cake. The frosting will begin to melt down a bit as you spread it on the hot cake, but it will set as it cools.
10) Let the cake stand in the pan on a cooling rack for 3 to 4 hours, or until completely cool. The frosting should be set and softly firm.
11) Sprinkled the top of the cake slightly with cocoa powder and garnished with chopped pistachio.

Coca-Cola Frosting

Ingredients:
3 ¾ cups plus 2 tablespoons icing sugar, sifted
Large pinch of salt
8 tablespoons (1 stick) unsalted butter, melted and cooled to tepid
2 ounces unsweetened chocolate, melted and cooled to tepid
1 ¼ tsp vanilla extract
6 tablespoons Coco-Cola, at room temperature

Method:
1) Combine the icing sugar and salt in a large mixing bowl.
2) In a small bowl, whisk the butter and melted chocolate until smooth.
3) Blend in the vanilla extract. Pour the chocolate mixture over the icing sugar, add the Coca-Cola, and beat on a low speed for 1 ½ to 2 minutes, or until just combined and smooth, using an electric hand mixer.
4) Scrape down the sides of the mixing bowl frequently to keep the frosting even textured.
5) Use the frosting immediately, or press a sheet of plastic wrap directly onto the surface. The prepared frosting can be made about 15 minutes before using. It will firm up as it stands.