In a large pan over medium heat, heat the olive oil.
Add the onions, carrot, celery and garlic. Cover and cook for 10 minutes until soft. Add the sugar, salt, pepper and tomatoes. Stir and cook for another 5 minutes.
Add the stock and bring to a boil, then simmer for 10 minutes. Transfer the soup to a blender and blend for about 1 minute until smooth, or if you have an immersion blender (produces much smoother results) blend until smooth, about 2 to 3 minutes.
Top with garnish and grilled cheese croutons.
Grilled Cheese Croutons
While soup is simmering, In a grilled cheese maker or on a skillet, prepare grill cheese sandwich to your likening until very crisp. Cut into cubes and add a few to soup immediately before serving.