Sauté the Aromatics: In a large skillet over medium heat, cook the chopped onion until soft. Add garlic and sauté for another 30 seconds.
Cook the Mushrooms: Stir in the sliced mushrooms and cook until they release moisture and become golden brown.
Create the Sauce: Sprinkle the flour over the mushrooms and stir well. Slowly add the chicken broth, stirring constantly to prevent lumps. Mix in Dijon mustard, paprika, salt, and pepper.
Add the Creamy Element: Reduce the heat and stir in the sour cream, ensuring a smooth, creamy sauce. Let it heat through without boiling.
Serve and Garnish: Spoon the stroganoff over cooked egg noodles or rice, then garnish with fresh parsley. Enjoy warm!