You can make hundreds of these simple little hearts from a piping bag of royal icing. They save well if packaged carefully on waxed or parchment paper in a large ziplock bag. They are perfect for simple cupcake toppers and make cute accent decorations on a cake.
Royal icing is the kind of frosting that becomes very smooth and hard when it dries. It's often used to create intricate designs on sugar cookies and typically the "glue" that holds together a gingerbread house. It's very simple to make. The key is to store it in an air-tight container with a piece of plastic wrap touching the surface. If the icing is in contact with the air, it begins to harden --- exactly what you want when you're creating hearts, a tiara (more on that later), or decorating a cookie, but not what you want if you need to keep the icing soft until you're ready to use it.
3 tablespoons meringue powder*
4 cups powdered sugar (about 1 pound)
6 tablespoons warm water
*I use Wilton brand meringue powder. The recipe above is also the Wilton recipe for royal icing. You could make it with egg whites, but this method is much simpler (and doesn't run the risk of food-born illness).
Beat all ingredients with an electric mixer until icing forms peaks (it will take about 10 minutes).
Once the icing holds peaks, you've reached a stiff consistency. This is perfect for gingerbread house glue, but too stiff for frosting hearts. You'll need to add water one teaspoon at a time until you reach a consistency that will spread a tiny bit when piped from a pastry bag, but won't spread too far. It's best to take a bit of the stiff consistency frosting and experiment with it until you get a feel for what you'll need to create these hearts. You could also use gel/paste food coloring to create any color you desire.
Then using a round tip on a piping bag, hold the piping bag with the tip at about a 45 degree angle above a piece of parchment paper (or waxed paper) and squeeze a bit of icing onto the paper. Move the tip down diagonally to the right slightly reducing the amount of squeezing as you move down. Stop squeezing and lift the tip away from the paper. That's the left side of the heart.
Repeat that same process to make the right side of the heart. Just move down and diagonally left, meeting the end of your first part of the heart.
That's it! If you're icing is the right consistency, the two sides will blend together slightly and smooth over as they harden creating a perfect heart. Let them dry completely overnight before using them. Carefully peel the hearts from the parchment paper.