This easy, one-bowl chocolate heart cake is moist, delicious and all dressed up in Valentine 's Day clothes!
Preheat oven to 325˚F. Spray an 8-inch round pan and an 8-inch square pan with baking spray. Wipe with a paper towel, to ensure the entire pan is coated with spray. Spray pans again lightly and line the bottom of each with parchment paper.
Combine butter, water and cocoa in a large microwave-safe mixing bowl. Cook on high power for 3 minutes, or until butter is mostly melted. Whisk well until smooth and lump-free.
Whisk in vanilla and sugar, then flour and salt, stirring until nice and smooth after each addition.
Bake for 35-40 minutes or until a toothpick inserted in the center of the cake comes out clean. Don’t over bake (my cakes usually take about 38 minutes, but every oven is different.) Allow cakes to cool in the pan, then turn out onto a work surface. Invert cakes so top surface faces up.
To make the heart shape, place the square cake on the diagonal on a large serving platter. Cut circle cake in half and place each half touching an upper edge of the square cake. (See pictures above in the post.)
Combine 4 ounces (1 stick) of butter and the chocolate chips in a large microwave-safe bowl. Cook on high power for 1 minute. Remove from microwave and whisk for 1 minute or until smooth and all chocolate chips have melted. (Return to microwave for 15-second intervals if chips have not melted after stirring.)
Add half and half (or milk) and vanilla. Whisk until smooth.
Add powdered sugar and salt. Whisk in the center of the bowl, bringing in more and more of the powdered sugar until mixture is smooth and all sugar is incorporated. If icing is super thick and hard to whisk, add a little more milk, 1 teaspoon at a time until smooth.
Finally, whisk in the very soft butter for about 30 seconds until icing is nice and fluffy.
Frost heart-shaped cake with prepared icing, starting at the top, working icing over the edges to cover. Sprinkle immediately with nonpareils, if using. Allow cake to sit for 30 minutes before serving to allow icing to set. See tips above in the post.
See Café Tips above in post for more detailed instructions and lots of tips.