Cook turnips and onions in steamer or boiling water until just tender. Drain. Whip thoroughly or put into blender. In large saucepan, heat milk and add turnips. Cook until milk is absorbed. (Watch and stir.) Cool. Add salt and pepper to taste. Fold into beaten egg whites. Pour into lightly buttered casserole. Bake at 350° until puffed and lightly browned. Even turnip-haters like this.