Bring a large pot of salted water to a boil for the egg noodles.

Season the beef strips generously with salt and pepper.

Heat the olive oil in a large skillet over high heat. Sear the beef in single layers for 1-2 minutes per side until browned but rare inside. Remove beef and set aside on a plate.

Reduce heat to medium and melt the butter in the same skillet. Add the sliced mushrooms and shallot. Sauté for 6-8 minutes until mushrooms are golden brown and moisture has evaporated.

Add the garlic and fresh thyme, cooking for 1 minute until fragrant.

Remove the pan from the heat briefly and carefully pour in the Cognac to deglaze, scraping up the browned bits from the bottom. Return to heat and simmer for 2 minutes to cook off the alcohol.

Stir in the beef broth and Dijon mustard. Simmer for 5-7 minutes until the sauce reduces slightly.

While the sauce simmers, cook the egg noodles according to package directions and drain.

Reduce the skillet heat to low. Stir in the crème fraîche until smooth and creamy. Do not let the sauce boil rapidly or the dairy may split.

Return the seared beef and any resting juices to the pan. Simmer gently for 2 minutes to warm the beef through.

Serve the stroganoff immediately over the hot egg noodles, garnished with chopped chives.