Cook the egg noodles in a large pot of boiling salted water according to package directions until tender. Drain, toss with 1 tablespoon of butter, and keep warm.

Pat the sliced halal beef dry with paper towels and season generously with salt and black pepper. Heat olive oil in a wide heavy skillet over high heat until shimmering. Sear beef strips in a single layer for 1 to 2 minutes per side until browned but still tender inside. Transfer immediately to a plate to prevent overcooking.

Lower heat to medium and melt remaining 2 tablespoons butter in the same skillet. Add sliced mushrooms and diced onions; sauté for 6 to 8 minutes until mushrooms are deeply caramelized and moisture has evaporated. Stir in minced garlic and cook for 1 minute until fragrant.

Sprinkle flour over mushrooms and stir continuously for 1 minute to cook out raw flour taste. Slowly pour in beef bone broth, scraping up all browned savory fond from the skillet bottom. Whisk in Dijon mustard and Worcestershire sauce; simmer for 4 to 5 minutes until sauce turns thick and glossy.

Turn heat to low. Gently fold in room-temperature sour cream until silky and smooth (do not boil after adding sour cream to prevent curdling). Return seared beef and any resting juices to the skillet, stirring gently for 1 minute just to re-warm through.

Ladle hot beef and velvety mushroom sauce over warm buttered egg noodles. Garnish generously with fresh chives, cracked black pepper, and serve immediately!