If you have one of the real candies, you can use it and Amazing Mold Putty to make a mold. Just follow the instructions on the mold putty package. (I've also got some mold-making tips here
.) Note: Mold the blank side of the heart, unless you actually want to copy the texture from the words.
Allow the mold to set. Once it's ready, press a 1/4 teaspoon ball of clay into the mold. Use a scraper tool or a clay knife to remove excess clay from the back. Pop the heart out and correct any molding flaws.
If you don't want to make a mold, you can easily hand-form the heart based on a real candy heart (or a photo of one).