In double boiler over low heat, melt chocolate.
When melted, turn off heat and let chocolate stand over warm water until needed.
In kitchen aide mixer bowl, combine cream and sour cream. Using whisk attachment, beat cream until thick and medium peaks form. Refrigerate until needed.
Place egg yolks in large heat proof bowl. In small saucepan combine "syrup" ingredients and bring to boil, boil 1 minute, stirring, until sugar has dissolved.
Whisk boiling syrup slowly into egg yolks then place mixture over double boiler and continue to whisk until mixture is thick and forms a ribbon when whisk is lifted, about 15 minutes. The mixture should almost triple in volume and be hot to the touch.
Remove yolk mixture from heat, place in kitchen aide mixer bowl and whisk mixture with kitchenaide on medium high speed until mixture has doubled in volume and cooled (the bowl should be cool to the touch). Fold warm chocolate into yolk mixture and combine well.
Fold in whipped cream mixture in 3 parts. Fold well to combine.
Place in a clean container. Label, date, initial and refrigerate.
Note: Must be chilled at least 2 hours to set up before use.