Cook pasta according to package directions, omitting salt and fat. Drain, and keep warm.
Preheat oven to 375°.
Place flour in a large saucepan. Gradually add 1/2 cup milk, stirring constantly with a whisk until blended. Stir in remaining milk. Place saucepan over medium heat; cook until thick (about 7 minutes), stirring constantly. Remove from heat; add cheeses, stirring until cheese melts. Stir in salt, mustard, and pepper. Fold in pasta, ham, and chives. Coat individual gratin dishes or a 13 x 9- inch baking dish with cooking spray. Spoon pasta mixture into dishes.
Pulse bread in a food processor until coarse crumbs form. Add oil, and pulse to blend. Sprinkle breadcrumb mixture evenly over pasta mixture and bake at 375° for 15 minutes or until mixture is bubbly and breadcrumbs are lightly browned. Serve immediately.