Preheat the oven to 350° F. Line cupcake pans with paper liners. In a medium bowl, combine the flour, sugar, baking soda, cocoa powder and salt; whisk to blend. In the bowl of an electric mixer, combine the eggs, vegetable oil, buttermilk, food coloring, vanilla and vinegar. Beat on medium speed until well blended. Mix in the dry ingredients on low speed and beat until smooth, about 2 minutes.
Divide the batter evenly between the prepared liners. Bake, rotating the pans halfway through baking, until a toothpick inserted in the center comes out clean, about 18 minutes. Let cool in the pans 5-10 minutes, then transfer to a wire rack to cool completely.
Once the cupcakes have cooled, crumble the cupcakes into a medium-sized bowl with your hands. Add 1/4 cup of buttercream frosting. Mix with your hands. You want the consistency of play-doh. Add more frosting if you need to.
Roll out the mixture onto a silicone baking mat or parchment paper lined cookie sheet to about a 1/4-inch thickness. Using a small heart cookie cutter, cut out the hearts for the center. Each cupcake needs two hearts. Place them on a plate or in a baking dish and store in your refrigerator until ready to use.