In saucepan, combine cream, chocolate, and sugar. Cook and whisk over medium heat until boiling and thickened, about 10 minutes.

Meanwhile, whisk egg yolks in medium bowl.

When chocolate has thickened, remove from heat. Whisk slooooowly into egg yolks, about 1/4 cup at a time (so you don't scramble the eggs).

Whisk in vanilla.

Pour into 4 small ramekins and chill 4-24 hours. If chilling longer than 4 hours, cover after chocolate has completely cooled.

Serve with chocolate shavings or whipped cream, if desired.