Cut the chicken into 1-inch pieces and season with garlic powder, salt and pepper. Dredge in flour, shaking off excess.
Heat 2 tablespoons olive oil in a large skillet over medium-high heat. Cook the chicken in two batches until browned and cooked through, about 3 minutes per side. Transfer to a plate.
Add the remaining 1 tablespoon olive oil and butter to the skillet. Add the mushrooms and onions. Sauté for 6-8 minutes until browned and any liquid has evaporated.
Stir in the Dijon, Worcestershire, and garlic. Cook for 1 minute.
Pour in the chicken broth and scrape up any browned bits. Return the chicken to the skillet and cook for 2 minutes.
Remove from heat and stir in the sour cream until combined. Season with salt and pepper.
Serve immediately over egg noodles, mashed potatoes or rice.