In a large stockpot, heat the oil over medium-high heat. Add the onions and cook for 5 minutes until soft. Add the garlic and cook for one more minute. Stir in the tomatoes, tomato paste if using, and chicken stock and bring to a boil. Reduce the heat to a simmer and cook for 20 minutes. Puree with a hand blender if desired. Stir in the thyme, oregano, bay leaf, sugar, salt and peppers. Simmer for 5 minutes. Add the heavy cream and basil. Taste for seasoning.