Chicken Medallions, Spinach, and Mushrooms au gratin

Start by slicing boneless, skinless chicken breasts into medallions 3/4-1" thick.  Season them with salt and pepper to taste.  Brown them in 6T butter in a saute pan.  Remove the chicken from the pan and make a roux with the butter by mixing in 1/4C flour.  Add 1/3C stock and 2/3C milk  stirring and deglazing the pan.  In another pan saute 8 oz. sliced mushrooms and 2 cloves minced garlic.  Add 1/2 lb. fresh spinach and gently saute until the spinach is just wilted.  Add the spinach mushroom mix to the sauce and fold in 1C grated cheese (we used asiago but use your favorite).  Layer the chicken medallions in a baking dish, covering each layer with the sauce.  Bake at 375 degrees for 30 min.  Finish with 5 min. under the broiler for a nice brown crust.  We served the dish with smashed red skin potatoes but rice would be nice as well.