Sardinian Clam Soup with Couscous

On a fine May morning in Sardinia I discovered three wonderful things. We were in Cabras, on the western coast, to have lunch, but we were early, so my husband and I decided to drive to the nearby beach of Is Arutas for a walk that we hoped would stir our becalmed appetites. We went as far as was permitted by car, and began to cross the seemingly scrubby ground that separated us from the beach. I looked down to see that, like a princess in a fairy tale, I was walking over what could have be