Cook macaroni per package directions, omitting salt; drain. Rinse in cold water;
drain and set aside.
Melt butter in a large skillet over medium-high heat; add carrots, celery, and
onion, and cook, stirring constantly, 5 to 7 minutes or until tender. Remove
vegetable mixture from heat; set aside.
Combine milk and cheese in a heavy Dutch oven, and cook over medium heat,
stirring often, until cheese melts. Stir in the bouillon granules and pepper.
Combine cornstarch and water, stirring well; stir into the milk mixture. Cook
over medium heat, stirring constantly, until mixture thickens and come to a
boil. Boil 1 minute, stirring constantly.
Stir in macaroni, vegetable mixture, corn, peas; and cook over low heat,
stirring constantly, until thoroughly heated.