Bring a large pot of salted water to a boil. Cook the wide egg noodles according to the package directions, drain them, and toss with a little butter or oil if they will sit before serving.

Pat the beef dry with paper towels and season it with approximately 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper. Heat the oil in a large skillet over medium-high to high heat, then sear the beef in batches for about 1-2 minutes per side, just until browned; transfer it to a plate before it cooks fully.

Reduce the heat to medium and add 2 tablespoons butter. Add the mushrooms and onion, cooking for 6-8 minutes until the mushrooms release their moisture and begin to brown and the onion softens.

Add the minced garlic and cook for about 30 seconds, just until fragrant. Stir in the remaining 1 tablespoon butter, sprinkle in the flour, and cook for 1 minute while stirring constantly.

Gradually whisk in the beef broth so the flour mixture dissolves smoothly. Add the Worcestershire sauce and Dijon mustard, then simmer for 3-5 minutes until the sauce thickens slightly.

Reduce the heat to low and stir a few spoonfuls of the hot sauce into the sour cream in a separate bowl. Return this tempered sour cream mixture to the skillet, stirring gently so it blends without curdling.

Return the seared beef and any accumulated juices to the pan. Warm everything gently for 1-2 minutes without boiling, then taste and adjust with additional salt and pepper.

Serve the creamy beef stroganoff over the cooked egg noodles. Finish with chopped fresh parsley if desired, and bring the skillet to the table while the sauce is warm and glossy.