Cook macaroni per package directions; 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.
Once vegetables are tender, stir in minced garlic and cook, stirring constantly, for about 1 minute.
Remove vegetable mixture from heat; set aside.
Combine milk, bouillon, and cheese in a heavy Dutch oven, and cook over medium heat, stirring often, until cheese melts.
Combine cornstarch and water, stirring well; stir into the milk mixture.
Cook over medium heat, stirring constantly, until mixture thickens.
Stir in macaroni, vegetable mixture, corn, peas; and cook over low heat, stirring constantly, until thoroughly heated.