If you can't find the dried French beans called flageolets, which have a lovely, subtle flavor, substitute navy beans.Plus: More Soup Recipes and Tips
In a medium bowl, soak the beans overnight in cold water to cover. Drain the beans and transfer them to a large saucepan. Add the onion, garlic, thyme and 6 cups of water and bring to a boil over high heat. Reduce the heat to low, cover tightly and simmer for 1 hour. Add 2 teaspoons of the salt and continue simmering, covered, until the beans are tender, about 20 minutes longer. Drain.
Transfer the beans, onion and garlic to the food processor and puree. Strain the puree into a saucepan, leaving the bean skins behind. Whisk 3 cups of the chicken stock into the puree.
Place the tomato cubes in a colander and sprinkle with the remaining 1 teaspoon salt. Let drain for 1 hour.
Preheat the oven to 300°. Put the bread cubes on a baking sheet and bake until dry and crisp, about 10 minutes.
In a large skillet, heat the olive oil. Add the bread cubes and cook over moderately high heat, tossing frequently, until browned, about 4 minutes. Transfer to paper towels to drain.
Shortly before serving, whisk the heavy cream into the soup and rewarm over moderate heat. If the soup is very thick, thin it with additional stock or water. Season with salt and pepper. Ladle the soup into warm soup plates and garnish each serving with some croutons, a cluster of tomato cubes and a few parsley leaves.
The recipe can be prepared through Step Two up to 2 days ahead. Let cool, then cover and refrigerate.