This recipe comes from Peter Miller's "Lunch at the Shop." It's great on its own, or also turned into what Peter calls "Pizza Soup." If you want to make the latter—and you should—simple fry some leftover pizza in a little olive oil to warm and to crisp the crust, then add a bit of Parmigiano and chopped basil to it. Remove the re-warmed piece of pizza from the skillet, use a good sharp knife to cut the pizza into strips, about 3/4-inch wide, and lay and poke them into the soup. Scrape whatever is left on the cutting board into the soup as well. Pizza soup!
Heat a small sauté pan over medium heat for a moment. Add 1 tablespoon of the oil, and heat for 1 minute. Add the sausage to the pan. The heat must be lively enough that they sizzle but not so intense that they burn—adjust it accordingly. Cook the sausages for 6 to 8 minutes, turning them several times while they brown and cook through (Alternatively, heat the oven to 375° F. Coat the sausages lightly in oil, place them on a rimmed baking sheet or roasting pan, and bake for 25 minutes. Do not prick the sausage—you want them to cook from within. Let them cool before slicing them into rounds). Remove them from the pan with a slotted spoon, and set them aside on paper towels to drain.
In a soup pot, heat the remaining 1/4 cup of the oil and the garlic over medium heat. Cook, stirring occasionally and keeping careful watch, until it is aromatic, 2 to 3 minutes. (If you brown the garlic, start over; the heat was too high, and the burnt taste will ruin the delicate soup.)
Add the beans, stirring them into the oil and garlic. Season with some salt and pepper, and cover the pan. You want to aromas to infuse the beans. Cook the beans, covered, for 3 minutes, and then stir in 1/2 cup of the stock.
Using a slotted spoon, remove about one-third of the beans and process them through a ricer back into the pan. This will thicken the soup. Gradually add the remaining stock the to mix, stirring and keeping the mixture at a simmer. The warm stock will loosen the soup, so add more or less to suit the consistency you desire. You will find the balance of the whole beans and the mashed beans and the liquid—that is your soup. Taste and season with salt and pepper, add the sausage and the parsley, and stir to combine.
The soup will keep in an airtight container in the refrigerator for 3 to 5 days.
When you reheat the soup at work, add 2 tablespoons of water to loosen its surface, then stir the top to combine everything evenly. Drizzle the top with a thin line of the oil just before serving.
Serve the soup with slices of soft white bread to sop it up, or serve it at room temperature as a side dish to a salad. Or, follow the directions in the headnote to make pizza soup.