In a stock pot, add the remaining 2 tablespoons olive oil and heat to medium heat. Add in the diced onion and the other 3 garlic cloves, minced. Cook for about 6 minutes until translucent and aromatic, stirring frequently. Add in the tomatoes, garlic and any juices from the sheet pan, the canned tomatoes with all the juices, chicken broth, basil leaves and salt and pepper. Stir well and bring to a boil. Lower to a simmer and let cook for about an hour.