Make sure the chocolate is high quality with 60-70% cocoa.
Use a 1:1 ratio for chocolate and heavy cream, adjust it according to the type of consistency you want.
Heat the heavy cream until it comes to a boil then immediately pour it over the chopped chocolate, avoid boiling it for a long.
Allow the hot cream to sit on the chocolate to make sure the chocolate melts properly.
Stir the mixture until smooth and glossy and check the runny consistency by dripping it on a bowl.