Bring a large pot of salted water to a boil. Cook the egg noodles according to package directions until al dente. Drain well and set aside. You can toss them with a teaspoon of butter to prevent sticking.

While the noodles cook, heat the olive oil in a large skillet or Dutch oven over medium-high heat. Add the ground beef and cook, breaking it apart with a spoon, until fully browned, about 5-7 minutes. Drain off any excess grease.

Add the chopped onion to the skillet with the beef and cook for 4-5 minutes, until softened and translucent. Add the sliced mushrooms and cook for another 5-7 minutes, until they have released their moisture and started to brown. Stir in the minced garlic and cook for one minute more until fragrant.

Sprinkle the flour over the beef and vegetable mixture. Stir continuously for about 1 minute to cook out the raw flour taste. Stir in the tomato paste until well combined.

Slowly pour in the beef broth while whisking constantly to prevent lumps. Stir in the Dijon mustard, Worcestershire sauce, paprika, salt, and pepper. Bring the sauce to a gentle simmer.

Reduce the heat to low, cover partially, and let the sauce simmer for 10-15 minutes, stirring occasionally, until it has thickened to your liking.

Remove the skillet from the heat and let it cool for 1-2 minutes. This is crucial to prevent curdling. In a small bowl, mix a few spoonfuls of the hot sauce into the room temperature sour cream to temper it. Then, stir the tempered sour cream mixture back into the skillet until the sauce is smooth and creamy. Do not return the skillet to a boil.

Serve the creamy ground beef stroganoff immediately over the warm egg noodles. Garnish with fresh chopped parsley.