Add chocolate and vanilla to a blender or a food processor.** Set aside.
Whisk milk, cream, egg yolks, sugar and salt together in a saucepan or pot until well combined.
Stirring continuously with a wooden spoon, heat the custard to a low simmer. Keep stirring until the mixture thickens and coats the back of the spoon (about 8 minutes).***
Pour the hot custard into the blender or food processor. Hold down the top if using a blender or hold down the feed tube if using a food processor. Process the mix until you have a uniform consistency (this will only take a few seconds).
Pour the mix into 4 jars (7-ounce capacity each) and chill until set (2-3 hours).
For the sweet coffee liqueur sauce:
Add cream and coffee liqueur to a saucepan and bring to a low simmer.
Stirring continuously with a wooden spoon keep the mix simmering until reduced to about ⅓ cup (about 7 minutes).
Let cool to room temperature.
For the espresso-flavored whipped cream:
Whip all ingredients to stiff peaks.
Top the pots de creme with the whipped cream and drizzle with the coffee sauce.
Notes:
*Please be sure to use baking chocolate bars and not chocolate chips or chocolate morsels for the pots de creme. Chocolate chips and morsels are often designed to keep their shape when heated and therefore have stabilizers in them. That prevents them from melting properly.**If you're using the food processor: If you have a whipping attachment on your processor use that, if not, use the regular s-shaped blade. ***Please watch this step closely, you do need to thicken the mix but you don't want to make scrambled eggs.