The method
- 01
Sear seasoned beef strips in screaming-hot butter, working in batches. Set aside.
- 02
Sauté onions and mushrooms in the same pan until deeply browned.
- 03
Deglaze with stock, simmer to reduce by half, stir in mustard.
- 04
Off heat, fold in sour cream and the rested beef. Toss with pappardelle.
