1. Preheat oven to 325 degrees.
2. Spray 3 8-inch heart shaped cake pans with non-stick spray, and line with parchment paper.
3. Prepare 2 boxes of cake mix according to directions on the box.
4. Divide cake batter evenly between 3 pans (pans will be about half full).
5. Bake for 25-30 minutes, until the cake feels firm when lightly pressed, or a toothpick inserted in the center comes out clean.
6. Allow cakes to cool to room temperature. Wrap cake layers in plastic wrap, and chill in the refrigerator until completely cold (a cold cake is easier to work with!) While cakes are chilling, prepare the buttercream:
7. In the bowl of a stand mixer fitted with the whisk attachment, combine powdered sugar, liquid egg whites, vanilla, and salt. Whip on medium speed for 2-3 minutes, until glossy and slightly thickened. Add the softened butter and continue to whip on medium until the mixture transforms into a fluffy buttercream, 6-8 minutes. Add food coloring a few drops at a time to achieve your desired frosting color.

Tip: For a smoother buttercream with fewer air bubbles, swap out the whisk attachment for the paddle. Scoop about one cup of buttercream into a microwave safe bowl, and microwave for 20-30 seconds, until the buttercream is “melted” and liquid–about the consistency of melted ice cream. Add this liquid back into the mixer bowl with the rest of the buttercream, and mix on medium-low with the paddle attachment until silky smooth.
 

Assembly

1. Unwrap cake layers. If cake layers are domed, use a serrated knife to slice the rounded top off the cake, so you are left with three even layers.
2. Place a cake layer in the center of a plate or cake board, and spread with a generous amount of buttercream.
3. On a clean work surface, use a 4-inch heart cookie cutter to punch out a heart shaped hole in the center of the second layer. Alternatively, cut a 4-inch wide heart out of parchment paper, and use it as a template to cut out a heart shape from the center of the layer with a knife. Now stack this layer carefully on top of the first layer.
4. Spread a thick layer of buttercream on the surface of the second layer, carefully avoiding the heart-shaped cavity in the center. If you have one, a piping bag can be very useful here! Fill the heart-shaped cavity with Brach’s Tiny Conversation Hearts, to the level of the frosting on the second layer. Invert the third cake layer (so the top/cut side is down) and stack it on top.
5. Cover the cake lightly with plastic wrap. Put the cake in the refrigerator for about 20 minutes, so the buttercream has a chance to firm up. This step will prevent your cake layers from sliding around as you decorate.
6. Remove the cake from the refrigerator, and cover with the remaining buttercream. Use the tube of red icing to write your favorite Conversation Heart message on top. Serve and enjoy!