Mix flour, salt and pepper together and coat chicken. Brown chicken in butter, set aside.
Slice mushroom, crush garlic. Sauté in butter until softened, add shredded fennel and fronds. Add Broth or Wine and simmer.
Whisk together sour cream and milk along with any flour left over from coating chicken. Slowly add to simmering mixture. Simmer until thickened slightly.
Pour sauce over chicken in pan. Let simmer for about 20 minutes on low.
Serve over rice or egg noodles.