Heat water bath to 176 degrees.
In a small saucepan, combine heavy cream and dark chocolate. Heat over medium heat until the chocolate is mostly melted, then whisk until very well combined and fully melted. Remove from heat and set aside.
Separate egg yolks and place into a large bowl or container. Add sugar and salt to the egg yolks and whisk together.
Add egg yolk mixture to chocolate cream mixture and whisk until very well incorporated. Ladle the mixture into jars (will make about 5 (8 oz) portions).
Carefully lower the jars into the bath with tongs or a spoon and cook for 90 minutes.
Remove from water bath and refrigerate for 6 hours up to overnight. Serve topped with whipped cream and berries (optional but makes it better).