Wash the clams under cold water and drain thoroughly. Discard any that are open or broken.
Heat the oil over a medium heat in a large saucepan. When hot, add the garlic and fry for a few seconds until it just begins to colour. Add the sherry or white wine and reduce by two thirds.
Add the clams and half the parsley, the beans and the saffron infused water, shaking the pan as you go. Simmer for about 2-3 minutes or until the clams are fully opened. Discard any clams that are still closed. Taste for seasoning.
Serve immediately with the remaining parsley, a drizzle of extra virgin olive oil and some bread to mop up the juices.