2 1/4 cups all-purpose flour
1 teaspoon baking soda
1/2 teaspoon salt
12 tablespoons unsalted butter, softened
1 3/4 cups granulated sugar
3 large eggs
1 1/2 teaspoons vanilla extract
3 ounces unsweetened chocolate, melted and cooled
1 1/4 cups buttermilk
Chocolate Buttercream:
4 1/2 cups confectioners' sugar, sifted
1/8 teaspoon salt
5 ounces unsweetened chocolate, melted and cooled
2 teaspoons vanilla extract
7 tablespoons milk, warmed to room temperature
8 tablespoons unsalted butter, cut into chunks and softened
Preheat oven to 350 degrees. Spray 2 9-inch cake pans with baking spray with flour. Sift the flour, baking soda and salt together onto a piece of waxed paper or into a bowl. Place the butter in the bowl of an electric stand mixer and beat at medium speed with a paddle attachment for 3 minutes. Add the sugar in 3 additions, beating for 1 minute after each addition. Scrape down the sides of the bowl well. Add eggs one at a time, beating until completely mixed in before adding the next one. Scrape down the sides of the bowl well. Beat in vanilla and melted chocolate. On low speed, added the flour mixture in 3 additions, alternately with the buttermilk in 2 additions. Scarpe down the sides of the bowl a few times to mix everything evenly. Divide batter evenly between the 2 pans, spreading it evenly. Bake for 30 minutes. Cool in pans for 5-10 minutes and then remove to a cooling rack to cool completely. Make Frosting. Place confectioners' sugar, salt, melted chocolate, and milk in the bowl of an electric stand mixer fitted with a paddle attachment. Scatter the butter pieces on top. Beat on medium-low speed for 2 minutes. Raise speed to medium and beat for another 2 minutes. Scrape down the sides of the bowl and then beat on high for 2 minutes. Add a little more milk if too thick.