Bribery Cake

This recipe is taken from Odette Williams ' Simple Cake, a collection of affordable and delicious cakes to celebrate every day. According to Williams, this cake is "a not - too-sweet chocolate sponge cake topped with silky Swiss meringue buttercream and sprinkled with a little sea salt: it's a cake that you bake to help yourself or a loved one cross the finish line."
Preheat the oven to 350°F. Prepare the form. If you are making cupcakes, cover the muffin tins with paper tinfoil tins (tinfoil tins are more durable because the dough turns out to be runny); do not fill the tins more than half fullPrepare the chocolate dough for the chocolate cake. Place a large sieve in a large mixing bowl. Add flour, cocoa, baking powder, baking soda and salt and sift.Add the sugar and beat until smooth. In another large bowl, whisk the eggs, milk, butter, and vanilla together.Gradually add the wet ingredients to the dry ones and beat until the lumps disappear and the dough is smooth. Carefully pour in the boiling water and stir until smooth. (Watch the kids fill up the hot water!)Bake the 9-inch square pie for 35-40 minutes, and the cupcakes for 20-25 minutes, or until a wooden skewer inserted in the middle comes out clean and the pie bounces off when lightly pressed.While the cake or cupcakes are being baked, prepare the buttercream for the chocolate Swiss meringue. Cut the butter into tablespoons. Pour about 1 1/2 inches of water into a medium saucepan, bring to a boil, then reduce the heat to maintain a low simmer.Place the egg whites, sugar, tartar, and salt in a metal mixing bowl (use the bowl of a stationary mixer if you have one). Place the bowl on a saucepan. Make sure that the bottom of the bowl does not touch the water. Beat the mixture continuously for 4 minutes, or until it reaches a temperature of 160 ° to 165 ° F if using a candy thermometer. The sugar will dissolve and the mixture will become opaque, bubbly and very warm to the touch.Carefully transfer the hot bowl to an electric mixer. Using the whisk attachment, beat the mixture on high speed for 4 minutes or until it is white and fluffy, with protruding peaks, and more importantly, until the mixing bowl is no longer warm to the touch.While continuing to beat with the mixer, add the butter one tablespoon at a time. This helps maintain a stable temperature. Scrape off the edges with a spatula. Whisk together the vanilla and cocoa until smooth.Let the cake cool on a wire rack. Brush the top of the cake or the tops of the cupcakes with buttercream. Sprinkle with sea salt.