Cook pasta according to package directions. Drain; return pasta to pan.
Meanwhile, cut chicken into bite-size pieces. In a large skillet, heat oil over medium heat. Add chicken, Italian seasoning, the 1/8 teaspoon salt, and the 1/8 teaspoon pepper. Cook and stir until chicken is no longer pink. Remove chicken from skillet; set aside.
In the same skillet, melt 3 tablespoons butter over medium heat. Add onion and garlic; cook and stir until tender. Stir in flour. Stir in tomato paste. Add milk. Cook and stir until mixture is thickened and bubbly; reduce heat. Add cheddar cheese, stirring until cheese is almost melted. Remove from heat; season to taste with additional salt and pepper. Add cheese mixture and chicken to cooked pasta in pan; stirring to coat. Spoon pasta mixture into a 13x9x2-inch foil baking pan with lid.
In a bowl, stir together bread crumbs, Parmesan cheese, and the 3 tablespoons melted butter. Place crumb mixture in a plastic bag; seal bag. Cover pan with lid. Attach crumb mixture and serving directions to pan (below). Store in refrigerator.