Roughly chop one of the fennel bulbs, and juice it. If you do not have a juicer, blend or process with a little water and rub through a sieve to obtain fennel juice. Otherwise, grate the fennel over a bowl and sieve it to catch the juice. Slice the other into wedges.
Fry the onion in the olive oil, and then add the fennel, beans, courgettes and peppers. Cook, stirring until the vegetabl