After you sprinkle the heart-shaped sprinkles and the conversation hearts, use the back of the toothpick to push down every heart. I know, that sounds ridiculous, but if you don't, they'll fall off. Even though the chocolate is hot, unless you add a little bit of pressure to each sprinkle, the sprinkles won't stick. So, when you cut this Valentine's Day chocolate bark, the sprinkles will just fall off leaving you with no decorations.