1. Season the chicken pieces with garlic powder, salt, and black pepper. Lightly coat each piece in flour, shaking off any excess.

2. In a deep skillet, heat 2 tablespoon of olive oil over medium-high heat. Brown the chicken in batches, cooking for 3-4 minutes per side until golden and cooked through. Transfer the browned chicken to a plate and set aside.

3. Reduce the heat to medium and add 1 tablespoon of olive oil and the butter to the same skillet. Sauté the sliced mushrooms and chopped onion for 6-8 minutes, stirring occasionally, until they release their liquid and it evaporates, leaving the mushrooms nicely browned.

4. Stir in the Dijon mustard, Worcestershire sauce, and minced garlic. Cook for about 1 minute, allowing the flavors to meld and the garlic to become fragrant.

5. Pour in the chicken broth, scraping up any browned bits from the bottom of the pan. Return the browned chicken and any accumulated juices to the skillet. Simmer for about 2 minutes, allowing the flavors to meld and the sauce to thicken slightly.

6. Reduce the heat to low and let the pan cool for a moment. Then, stir in the sour cream until the sauce is smooth and creamy. Be careful not to let it boil, as that can cause the sour cream to curdle.

7. Taste the Rich Chicken Stroganoff and adjust the seasoning with salt and pepper as needed.