Bring plenty of water to the boil in a large saucepan (you need a lot of space for the veggies, to preserve the colour). Blanch the beans in the water for 4 minutes, the drain them in a colander and run them under tap water until cold. Leave to drain and dry. It is really important to make sure that they get completely cold so that they don’t continue to cook – no-one wants overcooked green beans! Repeat this with the mangetout, but only cook for 1 minute (see above note).