White Wedding Cake Batter:
Preheat oven to 350°F.
Combine all cake ingredients in a stand mixer and blend on low for 30 seconds.
Scrape down the bowl and mix on medium-high for 2-3 minutes.
Grease a 1/2 sheet pan and line with parchment paper.
Pour batter into pan, tap out air bubbles, and bake for 15-20 minutes until a toothpick comes out clean.
Allow to cool completely before cutting out hearts.
Marshmallow Buttercream:
Beat butter and powdered sugar together for 1-2 minutes.
Add vanilla extract and marshmallow fluff, beating for an additional 3 minutes.
Transfer to a piping bag.
Assembling Heart Cakes:
Use a heart cookie cutter to cut shapes from cooled cake.
Cut hearts in half horizontally.
Pipe marshmallow buttercream on one half and sandwich with the other half.
Freeze assembled hearts on a baking sheet for at least 30 minutes.
Chocolate Coating:
Melt 2/3 of the white chocolate wafers with cream or Crisco for thinner consistency.
Add red food dye to achieve desired color.
Coat frozen heart cakes with chocolate, ensuring all sides are covered.
Remove cakes using forks, let excess chocolate drip off, then place on a lined sheet to set in the fridge.
Melt remaining chocolate, pipe swirls on set cakes.
Store covered in the refrigerator.