I'm so confused...I have read so many answers to this question.
What is the ratio of chocolate to heavy cream for ganache to be used for
FROSTING? Is the ratio different if I use the ganache under FONDANT? Also, I've read people using sugar, butter, and vanilla in ganache. I thought it was just choc. and cream.
Please, any help will be appreciated.

If you want a thick, rich, fudgey ganache, use equal parts, by weight, of dark or milk chocolate and heavy cream. For white chocolate, you need to do two parts chocoalte to cream.

If you are making whipped ganache, you need two parts heavy cream to one part dark or milk chocoalte (again, by weight). For white chocolate, use equal parts.

Vanilla or liqueurs can be added for additional layers of flavor.

Butter is sometimes added to white chocolate to help it melt better.

Sugar is only needed if using unsweetened chocolate.