Cut off the fennel fronds and stalks, Chop 2 tablespoons of the fronds. Reserve.
Cut bulb in half lengthwise and thinly slice. Set aside.
Whit the heel of your hand, gently flatten the pork. On a sheet of wax paper, dredge the pork in flour, shaking off the excess.
In a large skillet, heat 1 T of the oil over moderately high heat. Add the pork and cook for 3 minutes on each side or until just cooked through. Transfer to a plate.
Add the remaining oil, onion, and garlic and saute until softened.
Add the sliced fennel and saute for 5 minutes, or until crisp-tender.
Add the apple and saute for 5 minutes more.
Stir in the broth, 1/2 cup water, salt and pepper and bring to a boil.
Reduce to a simmer, return pork to the pan and cook for 1 minute, until heated through.
Serve with sour cream and reserved fennel fronds.