1
Heat 1 tbsp olive oil in a large skillet over medium-high heat.
2
Sear the beef strips in batches until browned on both sides, about 1-2 minutes per side.
3
In the same skillet, reduce heat to medium and add 1 tbsp of butter and sauté the mushrooms until golden brown.
4
Add another tbsp of butter to the skillet and sauté the shallots with a pinch of salt and pepper until softened, about 3-4 minutes.
5
Return the mushrooms to the skillet and add the minced garlic and thyme. Cook for another minute, stirring occasionally.
6
Reduce heat to med-low. Add another tbsp of butter if needed, and sprinkle the flour over the mixture and stir to combine. Cook out the raw flour taste for a couple of minutes.
7
Deglaze the skillet with white wine, scraping up any browned bits from the bottom of the pan. Let the wine simmer for 2 minutes.
8
Pour in the beef broth, stirring to combine. Reduce the heat to low.
9
Stir in the sour cream, heavy cream, Worcestershire sauce, and Dijon mustard until smooth. Taste and adjust seasoning with salt and pepper as needed. Let the sauce simmer gently.
10
While the sauce is simmering, cook the pappardelle noodles according to the package instructions. Drain and toss with 1 tbsp of butter to coat.
11
Add the seared beef to the sauce and stir to warm through.
12
Serve the sauce over the buttered noodles. Garnish with freshly grated Parmesan cheese and chopped chives.