Season chicken pieces with salt and pepper. Heat olive oil and 1 tablespoon butter in a large skillet over medium-high heat. Add chicken and sear until golden and cooked through. Remove and set aside.

In the same skillet, add remaining butter. Sauté onions until translucent. Add garlic and mushrooms, cooking until mushrooms are browned.

Sprinkle flour over the mixture and stir for a minute. Gradually pour in chicken broth while stirring to avoid lumps. Let simmer to thicken slightly.

Lower heat and stir in sour cream until smooth and creamy. Return chicken to the skillet and simmer for 2-3 more minutes.

Serve hot over egg noodles or mashed potatoes. Garnish with chopped parsley.