Cook shredded cabbage, covered, in a small amount of boiling salted water for 15 minutes or until cabbage is tender; drain well. Set cooked cabbage aside, and keep warm.
Melt 3 tablespoons butter in a heavy saucepan over low heat; add flour, stirring until smooth. Cook mixture 1 minute, stirring constantly. Gradually stir in milk. Cook sauce over medium heat, stirring constantly, until thickened and bubbly. Stir in pepper.
Place one-third cracker crumbs in a lightly greased shallow 2 1/2-quart baking dish. Spoon half of cabbage over cracker crumbs. Pour half of sauce mixture over cabbage. Repeat layers, ending with cracker crumbs. Dot cracker crumb layers with 2 tablespoons butter. Cover and bake at 350° for 30 minutes. Serve warm in baking dish.