Clean the mussels very thoroughly under cold running water. Scrub well with a stiff brush, and scrape off any barnacles. Discard any that are open or have cracked or broken shells.
Heat 60 ml (2 fl oz) of the olive oil until very hot in the biggest pan you have, one with a tight-fitting lid. Add two-thirds of the chopped garlic; it will colour immediately. Throw in the mussels, put on t