How to Make It
In a large pot, heat 1 tablespoon of the oil over moderate heat. Add the sausages and cook, turning, until browned and cooked through, about 10 minutes. Remove. When cool enough to handle, halve the sausages lengthwise and then cut crosswise into slices.
Heat the remaining tablespoon of oil in the pot over moderately low heat. Add the carrot, onion, celery, garlic, and rosemary. Cook, stirring occasionally, until the vegetables start to soften, about 10 minutes.
Puree 4 cups of the beans with 1 1/4 cups of the broth in a blender or food processor. Add the puree to the pot along with the remaining 1 1/2 cups broth, the whole beans, bay leaf, and salt. Bring to a boil. Reduce the heat and simmer, partially covered, for 15 minutes.
Stir in the pasta. Cook the soup over moderate heat, partially covered, stirring frequently, until the pasta is done, 10 to 15 minutes. Remove the bay leaf. Stir in the sausage and the pepper. Cook until the sausage is warmed through, about 1 minute.