Put a large pan of salted water on the hob to boil for the pasta, when its boiling add the pasta and cook as per the instructions.
chop the onion and place this in a large non stick pan with a glug of sunflower oil to saute, we dont really want colour here, we just want to soften here and cook through, then add the chopped leeks and chopped courgettes and then shredded cabbage.
Let these cook down and you can add a bit of colour to add some flavour but you dont want a burnt taste to them. Add some salt and pepper and season well. Add the beans (as much as you like 1/2 to a whole can) and then your pesto to taste. I quite like alot and i find the pasta soaks it up, i choose to add some water too to let down the sauce as the pasta really wants to soak it up.
Check the seasoning again and its ready to serve.