Bean soup of any kind -- even this lighter-than-usual version -- is a wonderful idea when the temperatures drop below freezing, as they have on our Manhattan street corner. But don't box yourself in by just making soup. For me, the trick is to have a pot of fairly plain beans already cooked so that they can be used in all manner of dishes: paella-type rice and pasta e fagioli -- already a kind of soup -- for instance, with more ideas in a story from a few years ago. I generally cook dried beans (soaked for a few hours or overnight depending on how old and dry they are) in a pressure cooker with aromatic vegetables, an herb or two and a little olive oil, but sometimes -- as I did the other day -- I do it in a traditional Tuscan way: very, very slowly.
After soaking, I put the white beans into a heavy pot with lots of water, considerable salt (some say this is taboo, but not the Tuscans), a few sage leaves, a whole peeled clove of garlic and a couple of tablespoons of good olive oil. I brought this to the simmer over a tiny flame: Italian grandparents specify that it should take an hour for it to come up to temperature. Then I partially covered the pot and left it to barely simmer for as long as it took: I lost track of the time after two and a half hours, occasionally checking on the water level and adding liquid as needed. The result was excellent: perfectly intact but perfectly tender beans and a great olive-oil aroma. Not another universe compared with the pressure cooker, but certainly another continent. This is worth doing occasionally, especially with new-season beans, which won't take as long to cook.
Making the soup was a cinch, and I did it in advance: In olive oil, I sweated a bean-size dice of a medium leek, a carrot, half a celery stalk, a tiny clove of garlic and a bit of fennel bulb, salted and peppered of course and aromatized with a couple of chopped sage leaves. When the vegetables were just about tender, I added three cups of pre-cooked beans (for three good portions) and a similar volume of a mixture of vegetable stock and bean-cooking liquid and simmered for just a few minutes. I removed some of it to a container and pureed it with an immersion blender, but there's no imperative to do that. I set the soup aside until dinner time. (Seasonal note: Sure, you can use some of that turkey stock your post-holiday fridge is full of.)
Also in advance, I cut a small dice of the caps from around half a pound of shiitake mushrooms (if I'd been prescient, I'd have used the tough stems in my vegetable stock - and of course I could have used other mushrooms too) and minced two medium shallots; these I salted and cooked in olive oil until lightly browned and tender, then added a slivered leaf of fresh sage and some black pepper. I did not add this to the soup, but set the little pan aside.
For serving, I reheated the soup, checked it for seasoning and added freshly chopped parsley and sage. Once I'd ladled out our bowlfuls of soup, I topped each with a mound of reheated shiitakes. I was going to drizzle on some good olive oil too, but tasting proved this superfluous.
Served with bread and butter - -either sturdy sourdough, grilled, or good baguette crisped up in the oven -- this is a perfect cold-weather dinner, especially with the mushrooms adding their own brand of savoriness. Plus, you've got all those unused beans on which to build more perfect dinners.