Cook the beans in boiling water and drain. Whether you decide to remove the skins of the beans will depend on their age and personal choice.
Heat the oil in a frying pan and cook the diced bacon until crisp. Remove with a slotted spoon and drain.
Wipe out the frying pan and return to the heat. Melt the butter over a moderate heat, then add the onion and garlic. Stir and cook unt