Place the chopped chocolate in a medium bowl with the coffee, salt, and vanilla and set aside
In a small saucepan, heat the cream over medium heat until a few bubble forms around the edge.
Pour the hot cream over the bowl with the chocolate. Let stand for 5 minutes to melt the chocolate, then whisk until combined.
Whisk egg yolks and sugar thoroughly and combine with the chocolate and cream.
Add the mixture to the saucepan and cook over medium heat, stirring constantly until the mixture coats the back of the spoon, about 4 minutes.
Divide among ramekins or dessert dishes, cover with plastic wrap, and refrigerate until cool and slightly firm (anywhere from 1 to 3 hours (different chocolates take different times to set back up after melting).
Notes
Use good quality chocolate that is no less than 54% Cacao to avoid problems with the pots de creme setting.
Boiling can cause a skin to form on cream so try to heat until just before boiling point.
If you use sweeter chocolate you may want to omit the sugar.