Partridges with Cockles in a Cataplana

This is a Portuguese recipe which Johnny gave me. It’s an unusual dish but surprisingly good. A cataplana for those of you who don’t know is a Portuguese double saucepan which locks closed, and which you can turn over to apply heat to either side. It is reputed to be the precursor to the pressure-cooker and is particular to the Algarve coast, so you may have picked one up on vacation; otherwise use a heavy pan for which you have a tight-fitting lid. Piri piri