In a kettle over medium heat, sauté the onion in the oil until lightly browned, about 10 minutes. Stir in the tomato paste. Reduce heat and cook 1 minute, stirring. Add water, bouillon, salt, pepper, bay leaf, thyme, and sugar. Cook 5 minutes, uncovered.
Add up to 2 cups of solid leftovers—carrots, celery, potatoes, peas, snap beans. These may be raw or cooked. If raw, mince or slice very thin, and cook 5 to 10 minutes or until tender before adding. If cooked, simmer about 5 minutes before serving. Cooked fish or meats may be added: beef, hamburger, chicken, turkey, and veal are good. Cube before adding and cook 5 minutes before serving.
Frozen vegetables, meats or fish may also be added. Cooked dishes may be added—rice dishes, stews, pasta leftovers, creamed vegetables, and mashed potatoes. Raw spaghetti, noodles, and rice work well, but these will require simmering 12 to 15 minutes, covered.
Add up to 2 cups liquid: milk, cream, buttermilk; any leftover soup that isn’t “cabbagy"; the cooking water of vegetables, tomato juice, gravy, wine, etc.
Taste and season: add more salt, pepper, sugar, paprika, wine, Worcestershire sauce, or those herbs that go so well with tomato-flavored soups—oregano, basil, and rosemary—1/4 teaspoon each (dried) is sufficient. Cook 5 minutes after the final seasonings have gone in, then serve.