Cook rutabaga slices, 1/2 teaspoon salt, and sugar in boiling water to cover in a Dutch oven over medium heat 45 minutes or until tender. Drain rutabaga well, and place in a large bowl. Beat at low speed with an electric mixer until mashed.
Melt butter in Dutch oven over medium heat. Whisk in flour and remaining 1 teaspoon salt until smooth, and cook, whisking constantly, 1 minute. Gradually add milk, whisking constantly. Cook, whisking constantly, 2 minutes.
Beat egg yolks until blended; gradually stir 1/2 cup hot milk mixture into yolks. Stir into remaining hot milk mixture, and cook 1 minute. Stir in mashed rutabaga, and remove from heat.
Beat egg whites at medium speed with an electric mixer until stiff peaks form. Fold into rutabaga mixture, and spoon into a lightly greased 11- x 7-inch baking dish. Sprinkle with bacon.
Bake at 350° for 40 minutes or until golden brown.
*6 medium turnips, peeled and sliced, may be substituted for rutabaga.