Heat the olive oil in a large skillet over medium heat. Add the chopped onions and minced garlic, sautéing until the onions are translucent, about 2-3 minutes.
Add the chicken strips to the skillet, seasoning with salt and pepper. Cook for about 5-7 minutes, or until the chicken is browned and cooked through.
Stir in the sliced mushrooms and cook for an additional 4-5 minutes until the mushrooms are tender.
Sprinkle the flour over the chicken and mushroom mixture, stirring well to combine. Cook for 1-2 minutes to eliminate the raw flour taste.
Gradually pour in the chicken broth, stirring constantly until the mixture thickens.
Lower the heat and stir in the sour cream and Dijon mustard until well blended. Heat through, but do not bring to a boil. Adjust seasoning if necessary with additional salt and pepper.
Serve the creamy chicken stroganoff over cooked egg noodles or rice, garnished with chopped parsley for a fresh touch.