Bone fish (or have your market do this chore), wash, and dry well. Sprinkle with salt and pepper. Roll in flour.
Brown 4 tablespoons of the butter in a frying pan and cook fish about 5 minutes on one side over moderate heat. Turn and brown the other side. Place on a warm platter.
Melt the other 2 tablespoons of butter and add to it a little nutmeg and the sage. Heat until butter has absorbed flavors of spices, but do not allow butter to brown. Pour over fish.
Garnish with sprigs of parsley and slices of lemon.