Cook macaroni in rapidly boiling water until not quite tender. Drain and reserve. Heat butter in a saucepan an cook the onion until tender, but not browned. Stir in flour, salt and pepper. Slowly add the cream and wine. Cook over low heat, stirring constantly, until thickened. Add cheese and stir until melted. Combine the macaroni and cheese and mix well. Bake at 350 degrees F for 15-25 minutes or until thoroughly heated through and bubbly.