Make the Cake

Cup of Yum
1. Preheat oven to 350°F.
2. Spray two 9-inch cake pans with cooking spray. Use the bottom of the cake pans to draw a circle on two sheets of parchment or wax paper. Cut the circles out and place them in the cake pan. Spray again with cooking spray, including the sides of the pan. Sprinkle flour on the inside of the pans and shake off any excess. Set aside.
3. In a bowl, whisk together the flour, cocoa powder, baking soda, baking powder, and salt.
4. In a large bowl (preferably in a stand mixer), beat the butter on medium speed for 30 seconds. With the motor still running, gradually add in the sugar, about ¼ cup at a time, until fully combined, stopping to scrape the bowl down a time, or two. Beat for 2 more minutes until fluffy and pale.
5. At the eggs, one at a time, waiting until fully incorporated before adding the next. Add in the vanilla and mix until combined, about 30 seconds.
6. Slowly add ⅓ of the flour mixture into the bowl with the mixer on medium-low. After fully combined, pour in half of the milk. Once combined, add another ⅓ of the flour mixture. Then the rest of the milk, and finally the last of the flour mixture. Turn the mixer on medium-high and mix for another 30 seconds.
7. Evenly pour the batter into the prepared pans. Bake for 30 to 35 minutes. (If using 8-inch pans, bake for 35 to 40 minutes). Once an inserted toothpick comes out clean, remove the pans from the oven and place them on a baking rack for 10 minutes. Run a clean knife around the edges of each pan and then carefully invert the pans onto the rack. Remove the parchment (or wax) paper and let the cakes cool completely before icing (usually about 30 minutes).

Make the Frosting

1. In a medium-sized saucepan (3 to 4-quart), melt butter over medium heat. Add the chocolate chips and stir until melted and fully combined. Let cool for about 5 minutes.
2. Stir in the sour cream. Gradually add the powdered sugar and use a large wooden spoon to incorporate it into the mixture. Continue stirring until smooth and all the lumps are gone (this takes a little elbow grease. You could also do this with a hand mixer on low).

Finish the Cake

1. Carefully place one of the cakes on a cake stand or dish.
2. Use a small spatula, or straight edge spreader, to apply about 1 to 2 cups of the frosting to the top of the cake (this will be the middle of the cake).
3. Carefully place the second cake on top of the frosted cake bottom. Apply the rest of the frosting to the top and sides of the cake. Use a straight-edge spreader to smooth the sides of the cake. Serve at once, or cover until ready to serve.