Something simple to make and serve cold on a summer evening.
Wash, scrub and beard the mussels. Change the water several times. Put them into a large pan, cover and shake it on a hot flame. When they have opened, take them off the fire, discard the upper shells, and arrange the mussels in their half-shells on a large flat white dish. Strain and reserve the liquor.
Prepare a sofregit by heating the olive oil in a pan, hash the onions very fine and slowly brown them in the oil. Add the tomatoes peeled and crushed, simmer for half an hour on a low heat while the liquor from the tomatoes evaporates. Then pour