Cockles live in sandy muddy areas so often found along estuaries. At low tides they are easiest to find. I like to look for an occasional ‘squirt’ of water from the mud. They tend to be pointing hinge down, opening up so finding a shell on its side is mostly fruitless. Make sure the diameter across the shell is more than 2cm – if it is less, then put the cockle back. As they live in sediment, they need purging to remove any grainy bits from their shells so I put them in a bowl of fresh water with a good amount of table salt and leave them over night. Once purged, cook them by heating under the grill, pan frying, adding them to a dish such as chowder and the heat will cook the meat and cause the hinged shell to open. As with mussels, if the shell is open when collecting then leave it and if it doesn’t open after cooking then discard it.