Mix the cake mix according to the package directions.
Spray the pan with cooking spray. Then fill the heart shapes in the pan with batter, about 2/3 of the way full.
Bake according to package directions for cupcakes, or until a toothpick inserted in the center of the cakes comes out clean.
Remove the cakes from the pan and let cool on a wire rack.
Filling-
Mix together the cream cheese, butter, and vanilla.
Add the powdered sugar, mixing well.
Then add in Marshmallow Fluff, making sure all the ingredients are mixed.
Once the cakes have cooled, slice them in half horizontally, add a layer of creme, and sandwich them back together.
Coating -
Melt the pink candy melts, according to package directions. See Notes below.
Gently dip (or roll) the cake sandwiches, one at a time, in the melted candy coating.
Set each dipped cake on wax paper. You may need to spoon a bit of candy coating on top of each cake once you've set it on the wax paper.
Once all the heart cakes have been coated, allow them to chill in the refrigerator until the coating has hardened.
Then melt the white candy melts, according to package directions.
Drizzle over the top of each cake in whatever pattern you desire. I used a bottle with a cake tip for this step.
Again, allow to chill until the candy coating has fully hardened.
Store the pink heart snack cakes in the refrigerator until ready to serve.
Notes
It can be difficult to shake excess candy coating off the cakes as you're dipping and rolling, and the coating may need to be just a bit thinner; it may help to add a tablespoon of shortening to it during the melting process.