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 the 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. Add eggs and whisk until completely incorporated.

Sprinkle baking soda over the top of the batter, then add buttermilk. Stir well.

Tap the bowl several times to bring air bubbles to the surface then divide the batter between prepared pans, trying to make the depth of the batter the same in each pan. The square pan will hold a little more batter (see the note above in the post).

Bake for 35-40 minutes or until a toothpick inserted in the center of the cake comes out clean. Don’t overbake (my cakes usually take about 38 minutes, but every oven is different.)

Allow cakes to cool for 10 minutes in the pan, then turn out onto a work surface. Invert cakes so the top surface faces up.

Cool completely before cutting and icing.

Place the chocolate pieces in a large microwave-safe bowl and microwave for 1 minute on power level 5 (50%).

Remove from the microwave and stir. Return the bowl to the microwave and cook for 20-second increments, stirring in-between, until the chocolate is mostly melted.

Remove from the microwave and stir until smooth and completely melted.

Whisk in the cocoa until smooth. Add the soft butter and whisk vigorously until well combined. Add the sour cream, half and half and vanilla. Keep whisking until smooth and creamy.

Add the powdered sugar, 1 cup at a time, whisking after each addition until smooth.

You should end up with a smooth, satiny, spreadable icing. If it seems a little thin, add a bit more powdered sugar. If it’s a bit thick, you can thin it at this point with more half-and-half.

To make the heart shape, place the square cake on the diagonal on a large serving platter. Cut the circle cake in half and place each half touching an upper edge of the square cake. (See pictures above in the post.)

Frost the 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 the tips above in the post.