On a pan, High heat, add 1 tsp butter to foam, add beef. Don’t move the beef. Cook both side to brown.
Medium heat, 1tsp butter, add mushroom
Medium heat, 1tsp butter, add onion to stir and then garlic.
Add vinegar and scape up brown bits at bottom of pan. When vinegar almost evaporated, add wine and continue deglazing the pan.
When wine is almost evaporated, add beef stock and bring to a simmer. When reduced to half, add cream and stir until it is thick
Put back the beef and mushroom to the pan and mix gently. Add in sour cream, mustard, pepper and salt. Then sprinkle chives and parsley