This is King Arthur’s Flour Recipe of the Year.
2 cups flour
1 1/4 teaspoons salt
2 teaspoons baking powder
4 large eggs
2 cups granulated sugar
1 tablespoon vanilla extract
1/8 teaspoon almond extract
1 cup milk (whole milk preferred)
4 tablespoons butter, cut into pats
1/3 cup vegetable oil
1 1/4 cups cocoa powder (sifted if lumpy)
1 cup + 3 cups confectioners’ sugar (sifted if lumpy)
1/4 teaspoon salt
1/3 cup hot water
1 tablespoon vanilla extract
16 tablespoons (1 cup) butter, softened
To make the cake: Preheat the oven to 325°F with a rack in the center. Lightly grease two 8” x 2” or 9” x 2” round cake pans; for extra protection against sticking, line the bottom of the pans with parchment rounds (you can cut these yourself or use precut 8” or 9” rounds), and grease the parchment. If your 8” pans aren’t at least 2” deep, use 9” pans.
In a small bowl, combine the flour, salt, and baking powder. Set aside.
In a large mixing bowl, either using an electric hand mixer or a stand mixer with whisk attachment, beat the eggs, sugar, vanilla, and almond extract, if using, until thickened and light gold in color, about 2 minutes at medium-high speed. If your stand mixer doesn’t have a whisk attachment, beat for 5 minutes using the paddle attachment. The batter should fall in thick ribbons from the beaters, whisk, or paddle.
Add the dry ingredients to the mixture in the bowl and mix — by hand or on low speed of a mixer — just enough to combine. Scrape the bottom and sides of the bowl, then mix again briefly, to fully incorporate any residual flour or sticky bits.
In a saucepan set over medium heat or in the microwave, bring the milk just to a simmer. Remove the pan from the heat and add the butter and oil, stirring by hand until the butter has melted.
Slowly mix the hot milk-butter-oil mixture into the batter, stirring on low speed of a mixer until everything is well combined. Scrape the bowl and mix briefly, just until smooth.
Divide the batter evenly between the two pans. You’ll use about 2 3/4 cups (about 580g) in each.
Bake the cakes until a toothpick inserted into the center comes out clean and the top feels set, 26 to 30 minutes for two 9” pans, or 38 to 42 minutes for two 8” pans; a digital thermometer inserted into the center of the cakes should read 205°F. Remove the cakes from the oven, carefully loosen the edges, and allow them to cool for 15 minutes in the pans. Then turn them out of the pans and transfer them to a rack, right-side up, to cool to room temperature.
To make the frosting: In a large mixing bowl or the bowl of your stand mixer, stir together – by hand or mixer – the cocoa powder, 1 cup of the confectioners’ sugar, and the salt. Stir in the water and vanilla, scraping the bowl if necessary.
Add the butter and remaining confectioners’ sugar, stirring to combine. Using an electric hand mixer or a stand mixer with paddle attachment, beat the frosting at medium-high speed for 1 to 2 minutes, until lightened in color and fluffy, stopping halfway through to scrape the bottom and sides of the bowl.
To finish the cake: For the best-looking cake, do the frosting in two steps. First, spread a very thin layer of frosting around the sides and across the top; this is called a crumb coat. You should be able to see the cake through the frosting in spots, it’s that thin. Refrigerate the cake for 20 minutes to let this layer set. Again, skip this step if time is a factor.
Once the cake is chilled, use the remaining frosting to coat it thoroughly and evenly. If you have any leftover frosting, you can use it to pipe decorations on the top and/or around the base.
Store the cake, covered, at room temperature, or in the refrigerator if your kitchen is hot. Let it come to room temperature before serving.