Preheat the water bath to 160°F (71.1°C).
Heat the heavy cream and chocolate in a pot over medium heat, stirring occasionally to prevent burning. Cook until the chocolate is melted. Remove from the heat and add the remaining ingredients, then blend together until thoroughly combined.
Evenly distribute the mixture into the canning jars, leaving about a 1/2" (13mm) at the top. Screw the lids on the jars until they are finger tight, basically until you feel medium resistance when tightening using only your fingertips. This will allow some air to escape during the sous vide process and help prevent breakage.
Carefully place the jars in the water bath and cook for an hour.
Once cooked, remove the jars from the water bath and let sit on the counter to cool for 10 to 20 minutes. Place the jars in the refrigerator to finish cooling. They will last for up to several days.
The whipped cream can be made in a stand mixer or whipping siphon.
Combine all ingredients in a whipping siphon. Seal the siphon and shake vigorously to mix. Charge the siphon. Shake well, 4 to 6 times, and chill until ready to dispense.
Just before serving, combine all ingredients in a stand mixer and whip until soft peaks form.
Remove the lid from the pot de crème and set aside. Top each pot with a few pecan halves and whipped cream then serve.