This traditional Italian pasta dish with beans started as a humble peasant dish. I like to mash half of the beans so it makes a creamy sauce to coat the pasta. Note that the dried beans need overnight soaking.
Soak the beans in a big bowl of cold water for 10 to 12 hours.
Drain beans and place in the pressure cooker with the tomatoes, carrots, onion and celery. Add enough water to submerge the beans and vegetables by about 2cm. Add salt and close the cooker.
Turn the heat on high. When the cooker starts whistling, bring down the heat and cook for about 15 minutes. Remove from heat, release all the pressure and open the cooker. Check if the beans are soft; if not, cook for a further 5 to 8 minutes longer in the cooker but without the pressure.
Place half of the beans in a food processor with a ladle of cooking liquid. Puree till smooth.
Meanwhile, cook pasta in abundant salted water following packet instructions. Drain and transfer to a bowl with the whole beans. Add 2 tablespoons of mashed beans to each plate then top with beans and pasta. Drizzle with oil and serve.
Add a ladle of tomato sauce to the beans, some fried pancetta or spice it up with cayenne pepper.