Cook the broad beans in a pan of boiling water for about 4-5 minutes. Drain and rinse under cold water. Shell the beans and discard the skins, if necessary, very small, young beans will be fine as they are.
Put the beans, yogurt, mint, cheese and garlic (if using) into a food processor. Whizz until you have a thick green puree. Season to taste.
Serve the dip with a selection of colorful vegetable crudite.