Heat the olive oil in a pan, add the onion and gently fry for four minutes.
Add the cockles and white wine, cover with a lid and leave for 3-4 minutes or until all the cockle shells have opened.
Discard any that have not opened or the shells that are damaged.
Add the butter and garlic to the pan and cook for one minute.
To serve, place the toasted bread onto a serving plate. Pour the cockles and sauce over the bread.