Roughly chop the onions, roast them in butter until golden, dust with flour, pour in the clear soup, boil the sauce for 15 minutes, season with mustard, salt and juice of a lemon and stir in the whipped cream. Add finely chopped mushrooms and gherkins to the sauce. Cut the meat into strips or cubes (or into flat pieces) and fry at high temperature in a frying pan (approx. 2 min.). The meat must remain pink on the inside and must not be cooked through, otherwise it will taste leathery.
Mix the roasted meat with the sauce, add the meat and toss it briefly in the sauce, but do not bring it to a boil. If you wish, you can refine the sauce with sliced tomatoes (add them to the onions).
Serve with bread dumplings, fried potatoes, long grain rice or pasta.