Cut the onions into strips and briefly blanch them in boiling water, then strain.
Froth half of the butter and sauté the onions and parsley in it. Dust with flour, roast and deglaze with the beef stock while stirring. Cook for 30 minutes.
Strain through and season with salt, pepper and caraway seeds. Bring the cream and the remaining butter to the boil again briefly, then serve immediately.