Velouté
A velouté is one of the French mother sauces: stock thickened with a roux, and the technical name for the sauce inside most chicken pies.
Chicken stock whisked into cooked flour and butter, simmered until it coats a spoon, is a velouté whether or not anyone calls it that. Cream turns it toward a sauce suprême.
Knowing the name matters less than knowing the ratio: roughly 30g each of butter and flour thickens 400ml of stock to pie consistency.