Grease 8 x 8 pan. Boil 1/2 bag frozen spinach until thawed. Drain well. Saute 1/4 cup finely chopped onion. Beat 1 dozen eggs with wire whisk. Add salt, nutmeg, and pepper to taste. Mix in 3 cups milk and drained spinach. Pour into cake pan and bake 3/4 hour at 350 degrees, until toothpick comes out clean. Grate Swiss cheese on souffle; melt 5 tablespoons butter, crumble bread into butter and toss. Place souffle back in oven until bread crumbs are brown and melt cheese.