On page 181 of Hanna Winsnes’ cook book:
Take equal amounts of butter and thick sour cream. Brown the butter in a pan and mix in a teaspoon of flour; this should be mixed with a couple of spoonfuls of cooking juice. When boiling add the cream and stir vigorously until the sauce is boiling. If you don’t have any cooking juice, don’t use any flour either but then the cream has to be really good. Should it happen that it starts to separate, add a little more cream, and as it therefore will become too white, compensate with soy.
This gravy is for veal and roasted bird ad can in a pinch be used for roast beef or roast lamb. For roasted bird you should avoid the soy.