Preheat oven to 350° with the oven rack in the middle. Spray two
9″ round cake pans with cooking spray and line the bottoms with parchment
For the cake: In a small saucepan over medium heat, combine butter and 1 cup water
and heat until the butter is melted. In a medium bowl, whisk together the eggs, sour cream and vanilla. In a large bowl (or the bowl of a stand mixer), whisk together flour, granulated sugar, brown sugar, cocoa powder, baking soda, baking powder and salt. Add the butter mixture and use an electric mixer on low speed to mix
until just combined. On medium speed, mix in the sour cream mixture.
Dividing evenly, scrape the batter into the prepared pans. Bake for 30
to 35 minutes, until a toothpick inserted into the center of the cakes comes
out with a few moist crumbs attached. Place the pans on a wire cooling rack and
let cool for 25 minutes. Run a paring knife around the edge of each cake to
loosen it from the pan, then invert the cakes onto the rack, remove the
parchment, and let cool completely.
Make the frosting: Put the chocolate chips in a medium bowl. In a small
saucepan over medium heat, heat the cream until hot. Pour cream over chocolate and let stand for 1 minute. Now gently whisk until creamy and
Scoop out 3/4 cup of the chocolate mixture into another bowl and set
aside the remaining frosting for now. Let the 3/4 cup of the mixture cool,
stirring occasionally, for about 1 hour, or until it’s spreadable, creamy, and
holds its shape.
Place one cake on a serving plate, bottom side up. Spread the top with frosting in an even layer all the way to the edge, then top with the other cake,
bottom side up.
Gently reheat the remaining frosting by filling a medium saucepan with
2 inches of water and placing over medium heat. Let come to a low simmer. Place
the bowl of frosting over the water (the bottom of the bowl should not touch
the water). Stir until it is melted and pourable. Immediately pour the frosting
over the top of the cake. With a metal spatula, quickly spread it to evenly
cover the top and let the frosting drip down the sides. Once the frosting is
set, slice and serve.