In a small saucepan or the microwave, heat the cream just until hot.
Place the chopped chocolate in a medium bowl and pour the hot cream over it. Let stand for 5 minutes.
Whisk egg yolks thoroughly and combine with the chocolate and cream.
Add the vanilla, coffee and salt and whisk until smooth, then 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). You are looking for a spreadable consistency.
For a whipped frosting, using a mixer whip (or beat) the mixture at medium speed until light, fluffy and forms stiff peaks, about 3 minutes. Makes about 2 cups of frosting (enough for 12 cupcakes).
Cover the pots de creme with plastic wrap and refrigerate for at least 1 hour.
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.