Place the chicken breasts in the dish, coating each side with oil. Squeeze the juice of 1/2 lemon over all. Slice the rest of the lemon and place a lemon slice on top of each chicken piece.
Bake in the preheated oven for 30 to 40 minutes until brown.
In a large skillet, melt the 1/4 cup butter or margarine.
Add the sliced mushrooms. Cook and stir until the mushrooms are brown and have exuded their juices, about 6 minutes.
Sprinkle with the flour and blend.
Add the chicken broth, stirring to make a medium thick sauce. Allow to reduce, adjusting with a little more broth to make a creamy sauce.
Add fresh parsley at the last minute. Spoon the sauce over the lemon baked chicken breasts. Delicious!