Chocolate mom

When making large chocolate Easter eggs I find the seams ugly. I have tried piping tempered chocolate rosettes around the egg, but the chocolate is too runny to hold it’s shape. What do chocolatiers use? Is it chocolate royal icing, ganache or do I just let the chocolate cool to pipe? I am a housewife with no formal training in chocolate making, who has taught herself from google, so please forgive my ignorance.