Add onions, carrots and celery; cook and stir 5 min. Stir in broth and water. Bring to boil; cover. Simmer 10 min. or until vegetables are tender.
Add tomatoes and pepper; stir. Return to boil. Simmer 5 min. Stir in cream cheese and 1/4 cup basil.
Remove from heat. Use immersion blender to blend soup until smooth. Return to heat; cover. Keep warm on low heat while you prepare America's Favorite Grilled Cheese Sandwiches.
Cut each sandwich into 6 pieces. Ladle soup into 6 bowls; sprinkle with remaining basil. Top each soup bowl with 2 sandwich pieces.