Soak the chickpeas overnight. Cook them for 3 or more hours with the ham bone at a low temperature, just simmering. Sweat the celery and garlic. When they’re soft add nearly all the cooked chickpeas. Put the lot through the processor. Use chickpea water and oil to get a soupy consistency. Cook the pasta, add to the soup. Decorate with the remaining chickpeas – or don’t bother.