Season the sliced meat with salt and pepper and fry in hot oil or vegetable cream. Cut the onions into rings and add. Fry everything for about 5 - 10 minutes, stirring occasionally. Deglaze with a little soy sauce (approx. 1 - 1 1/2 tablespoon, otherwise it will be too salty). Now add the cream and bring to the boil briefly, then stir in the sour cream. Season to taste with salt, pepper and broth.
If the sauce is still too runny, you can mix a little milk with a maximum of 1 tablespoon of flour or cornstarch (there should be no lumps), add to the sauce and bring to the boil. If the sauce gets too thick, you can dilute it a little with a little milk.