Birthday Cake (Yellow Cake with Chocolate Frosting)

Adapted from SmittenKitchen.com

Note: If you don't have buttermilk, you can add 1 tablespoon of vinegar or lemon juice for each cup of milk instead [2 tablespoons of acid and 2 cups of regular milk total for this recipe].

4 cups plus 2 tablespoons all-purpose flour
2 teaspoons (10 grams) baking powder
1 1/2 teaspoons baking soda
1 teaspoon (5 grams) table salt
2 sticks (1 cup, 1/2 pound or 225 grams) unsalted butter, softened
2 cups (400 grams) sugar
2 teaspoons (10 ml) pure vanilla extract
4 large eggs, at room temperature
2 cups buttermilk (475 ml), well-shaken

Preheat oven to 350°F. Butter two 9-inch round cake pans and line with circles of parchment paper, then butter parchment. (Alternately, you can use a cooking spray, either with just butter or butter and flour to speed this process up.)

Mix together flour, baking powder, baking soda, and salt in a medium bowl. In a large mixing bowl, beat butter and sugar in a large bowl with an electric mixer at medium speed until pale and fluffy, then beat in vanilla. Add eggs 1 at a time, beating well and scraping down the bowl after each addition. At low speed, beat in buttermilk until just combined (mixture will look curdled). Add flour mixture in three batches, mixing until each addition is just incorporated.

Spread batter evenly in cake pan, then rap pan on counter several times to eliminate air bubbles.Bake until golden and a wooden pick inserted in center of cake comes out clean, 35 to 40 minutes. Cool in pan on a rack 10 minutes, then run a knife around edge of pan. Invert onto rack and discard parchment, then cool completely, about 1 hour, then frost.

Frosting

Makes about 2.5 cups

3 ounces unsweetened chocolate, melted and cooled
2 1/4 cups confectioners’ sugar
1 1/2 sticks unsalted butter, at room temperature
3 tablespoons  milk
1 1/2 teaspoons vanilla extract

Place all of the ingredients in a food processor and pulse to incorporate. Scrape down the sides, then process until the frosting is smooth.