1.Preheat oven to 400
2.Wash & drain the spinach.
3.Set a large covered pan on low, Add 1 tbsp butter then add spinach, cover until just wilted. Set aside.
4.In a medium sauce pan on low heat melt 2 tbsp of butter and then stir 3 tbsp of flour, one at a time. When done let cook for a 1 - 2 minutes.
5.Heat milk in microwave until hot but not boiling. Stir into butter/flour mixture a bit at a time, stirring constantly. When all the milk is in and the mixture has a smooth consistency add nutmeg and salt and pepper , set aside.
6.Set a frying pan on medium heat, add butter and wine, and bring to scant boil. Reduce heat if necessary.
7.Add sole, and spoon liquid over fillets. Poach for about 5 minutes - then remove and set aside.
8.Turn heat under the frying pan to high - and boil until the liquid has been reduced to about 1/3. Pour into reserved flour/butter/milk mixture.
9.Butter an ovenproof dish with the remaining butter, layer in the spinach completely covering the bottom of the dish. Put the sole on top, and then pour over the white sauce.
10.Sprinkle with Parmesan and place in oven for 20 minutes