Chop the beef into bite-size pieces.
Heat up olive oil in the pot and stir fry the onion until translucent.
Add the beef, garlic, and Shiitake powder and stir fry.
Add 1/2 Tbsp red wine vinegar and A, then simmer at low heat with the lid on for about 20 minutes.
Add the rest of the red wine vinegar and adjust the taste with salt and pepper.
Plate it up, garnish with finely chopped parsley, and serve with sour cream on the side.