1. Heat oil in large skillet. Season chicken with salt and pepper. Add to skillet; saute 6 minutes or until golden, turning halfway through. Remove to platter. Drain off all but 1 tablespoon drippings.
2. Place the skillet over medium heat. Add the mushrooms; saute for 5 minutes, turning over halfway through the cooking.
3. Return the chicken to the skillet along with the 1/4 cup chicken broth, the white wine and rosemary. Cover; simmer for 15 minutes or until the chicken is tender.
4. Whisk together the flour and the remaining 2 tablespoons of chicken broth in a small cup or bowl until smooth and well blended. Whisk into the skillet; cook, stirring occasionally, for 3 to 5 minutes or until sauce is thickened and bubbly. Stir in the sour cream; gently heat mixture through (do not let boil or the sauce may separate).