Cut boneless skinless chicken breasts into 1-inch pieces. Season with garlic powder, salt, and black pepper. Coat with flour.

In a large skillet, heat olive oil over medium-high heat. Add chicken and cook for 3-5 minutes on each side until golden brown.

Add more olive oil if needed, then add mushrooms and onion. Sauté for 6-8 minutes until the mushrooms are golden and the onions are translucent.

Stir in Dijon mustard, Worcestershire sauce, and minced garlic. Cook for about 1 minute.

Pour in chicken broth, scraping the bottom to deglaze. Return the chicken to the skillet and let simmer for 2 minutes.

Reduce heat to low, stir in sour cream, mixing slowly to avoid curdling. Adjust seasoning to taste.

Serve the creamy chicken stroganoff over egg noodles or mashed potatoes.