Directions

1. Heat oil in a large skillet over medium heat. Add onion and garlic and saute until slightly clear, then reduce heat to medium low (careful not to burn, but browning is okay).
2. Meanwhile, melt butter or margarine in another large skillet over medium high heat. Rinse chicken breasts and pat dry; season with salt and pepper to taste and brown on both sides, about 2 minutes each side.
3. Drain and add browned chicken breasts to onion/garlic mixture, then add rosemary, mushrooms and chicken broth. Stir to mix together, making sure chicken breasts are evenly spaced in the skillet. Reduce heat to simmer, cover skillet tightly and cook for 30 minutes.
4. Add sour cream and stir well, breaking up any clumps with a spoon. Cover skillet again and allow to heat through for 10 minutes.
5. Strain about 3/4 cup of the liquid from the skillet into a small bowl; add flour and mix well with a fork to break up any clumps. Pour mixture into the chicken mixture, stir well and cook over medium heat for about 15 to 20 more minutes to thicken the sauce. Serve hot.