Thaw the spinach and squeeze it dry. Mix the spinach, two kinds of cheese, flour and chopped scallions in a large bowl until thoroughly mixed. Beat the two eggs separately and add them to the spinach mixture. Melt the butter and mix it in. Pour into a 2-quart casserole and bake for 1 hour at 350 degrees. This dish can be easily doubled and tripled for holiday meals, and baked during the last hour to hour-and-fifteen minutes of cooking time for roasts, hams or turkeys.