How to Make It
Preheat the oven to 350°F. Prepare pan. If you are making cupcakes, line the cupcake pans with foil paper liners (foil liners are sturdier, as this batter is runny); don’t fill liners more than halfway
Prepare the Chocolatey Chocolate Cake batter. Place a large sifter or a sieve in a large mixing bowl. Add the flour, cocoa, baking powder, baking soda, and salt and sift.
Add the sugar and whisk until combined. In another large bowl, whisk the eggs, milk, oil, and vanilla together.
Gradually add the wet ingredients to the dry ingredients and whisk until there are no lumps and the batter is smooth. Carefully pour in the boiling water and stir until combined. (Watch the little ones with the hot water!)
Bake a 9-inch square cake for 35 to 40 minutes and cupcakes for 20 to 25 minutes, or until a wooden skewer inserted in the center comes out clean, and the cake bounces back when lightly pressed.
While the cake or cupcakes are baking, make the Chocolate Swiss Meringue Buttercream. Cut the butter into tablespoons. Fill a medium saucepan with about 1 1⁄2 inches of water, bring to a boil, then lower the heat to maintain a gentle simmer.
Place the egg whites, sugar, cream of tartar, and salt in the metal mixing bowl (use the mixing bowl of a stand mixer if you have one.) Place the bowl on top of the saucepan. Make sure the bottom of the bowl doesn’t touch the water. Whisk the mixture constantly for 4 minutes or until it reaches a temperature between 160° and 165°F if using a candy thermometer. The sugar will have dissolved, and the mixture will be opaque, bubbly, and very warm to the touch.
Carefully transfer the hot bowl to the electric mixer. Using a whisk attachment, beat the mixture on high speed for 4 minutes or until it’s white and fluffy with stand-up peaks and more importantly, until the mixing bowl is no longer warm to the touch.
With the mixer still running, add the butter a tablespoon at a time. This helps keep the temperature stable. Scrape down the sides with a spatula. Beat in the vanilla and the cocoa, until fully incorporated.
Cool cake on a wire rack. Ice the top of the cake or the tops of the cupcakes with the buttercream. Sprinkle with sea salt.
Reprinted with permission from Simple Cake by Odette Williams, copyright © 2019.