This sauce made with Vin Jaune ("yellow wine") is emblematic of Comtoise cuisine from Eastern France. It combines the smoothness of cream with the slight acidity and typical flavour of the Vin Jaune.
The tricky aspect of cooking with Vin Jaune is that its fugitive flavour tends to disappear when cooked for any length of time. You will notice that this recipe uses a particular way of finishing the sauce to limit this loss of flavour.