Put the dark and milk chocolates in a medium stainless steel bowl over a saucepan of simmering water and heat just until the chocolate melts, then transfer the warm chocolate to the bowl of a food processor. Meanwhile, heat the cream in a small saucepan over low heat just until it starts to simmer. Pour the warm cream into the warm chocolate and wait about 1 minute. Add the agave or honey and vanilla. Run the food processor. You’ll notice that the mixture will look speckled and separated, then will come together as a uniform ganache. Adjust the flavors to taste.