Preheat the oven to 350°F. Line one 9x13 baking sheet with parchment paper, or spray it with a non-stick spray.
In a large bowl, combine the vanilla cake mix, flour, sugar, salt, eggs, milk, vegetable oil, sour cream, and vanilla extract. Mix until smooth.
Pour the batter onto the prepared baking sheet and spread it into a thin, even layer. Bake for 15-20 minutes, or until a toothpick comes out clean. Let cool completely.
While the cake is cooling, make the whipped frosting center: Start by beating softened butter in a bowl until creamy. Add marshmallow creme, powdered sugar, salt, vanilla extract, and heavy cream. Mix until light and fluffy.
Line a 2nd baking sheet with parchment paper. Using a heart-shaped cookie cutter, cut the cake into hearts: Place the cut out pieces on the parchment.
Assemble the cakes by piping, or spreading frosting onto one heart and sandwiching it with another heart. Repeat for all pairs.
Melt white chocolate candy melts according to package instructions. Set aside a couple tablespoons of white chocolate and then stir in pink food dye into the rest to achieve desired color.
Dip each heart cake sandwich into the melted chocolate, covering it entirely. Let excess drip off.
Place the dipped cakes on parchment paper, then allow the cakes to harden. Finish with white drizzle to decorate the cakes.
Keyword cake, copycat, dessert, diy, frosting, little debbie, vanilla, whipped