Cut the chicken breast halves into 1-inch pieces and season with garlic powder, salt, and black pepper. Coat with flour.

Heat olive oil in a large skillet over medium-high heat and sear the chicken for 4-5 minutes on each side until golden brown. Remove and set aside.

In the same skillet, reduce heat to medium and add olive oil and butter. Sauté mushrooms and onion for 6-8 minutes until golden.

Stir in Dijon mustard, Worcestershire sauce, and minced garlic. Sauté for 1-2 minutes until fragrant.

Pour in chicken broth and scrape the bottom of the pan. Return the chicken to the skillet and heat through for 2-3 minutes.

Lower the heat and stir in sour cream gradually, avoiding boiling. Adjust seasoning with salt and pepper.

Serve warm over egg noodles, mashed potatoes, or with crusty bread.