Heat the olive oil in a large pot over medium high heat. Add the diced onion and sauté until it softens, about 3-4 minutes. Add in the minced garlic and cook for another minute.

Add in the canned tomatoes and season with salt and pepper. Using a potato masher, mash the tomatoes until they are all broken up. Add in the bay leaf, brown sugar, and chicken broth. Stir and bring the mixture to a boil.

Once the soup is boiling reduce the heat to medium low and simmer for 10 minutes. Pull out the bay leaf and remove from the heat. Pour half the soup into a blender or food processor and process until smooth.

Strain the soup and repeat the process with the second half. Return the strained soup to the pot and stir in the balsamic vinegar. Bring the soup back up to a simmer and cook for several more minutes. Serve the soup immediately topped with chives.