This recipe is so simple, it's amazing how delicious it is. If you have a sage plant growing, you probably have all the ingredients needed in your pantry. The flavors of sage, white bean, and truffle oil are divine, and so warming. Every bowl is a special experience. —raychalz
cannellini beans, or any white bean, soaked overnight
Soak beans overnight, or for at least 6 hours. In a pinch, soaking can be skipped, you'll just have to simmer the beans for longer until they're fully cooked. I think this is a perfectly acceptable alternative.
Trim the ends off the onion and remove the skin, but leave it whole. In a stock pot, at least a gallon in size, add 3 quarts of water, beans, the whole onion, fresh sage, oil, and salt. The amount of oil can be adjusted depending on the size of your pot, but the idea is to entirely cover the top surface of the water, and it's ok if some sage is sticking up through the oil "lid". The flavorful oils from the sage should end up infusing the oil and mixing beautifully into the finished soup, so reduce if you must, but don't exclude the olive oil. Bring to a boil, then reduce heat, cover, and simmer lightly until beans are cooked through, at least an hour.
When the beans are fully cooked, fish out the sage and the onion with a slotted spoon, and discard. Then, spoon out about half of the beans and set them aside in a bowl. (If you like a smoother soup, take out fewer beans, 1/4 - 1/2 is a good amount to leave whole). Puree the beans and broth that remain in the pot with an immersion blender until smooth. Add the reserved, whole beans back in. Adjust salt to your liking, add pepper if desired.
Ladle into a bowl, and drizzle with a little bit of truffle oil, about 1 Tablespoon per bowl, enough to make an attractive spiral. The flavor of truffle oil goes a long way with only a small amount. If you have extra sage, it makes a pretty garnish. Sometimes, I'll fry a few of the extra leaves in hot vegetable oil for about twenty seconds to make a crispy, delicious, classy looking garnish, but the truffle oil alone is pretty enough. Enjoy!