One of Portugal's favourite ingredient is Bacalhau. For those who don't know what this is, it's a fish. Cod, to be more precise. But in Portugal, cod isn't consumed fresh. The cod that is preferred has been salted and dried. To cook it, it has to be rehidrated and this is what I'll be explaining next.
To rehidrate the cod, it has to be cut into pieces as shown in this image
These pieces are then to be soaked in cold water for 24 to 48 hours, depending on the size of the fish, taking care to change this water every 6 to 8 hours. If the water isn't changed, it will start to smell bad and ruin the fish. This process serves, not only to rehidrtae the fish, but also, to extract the excess salt. If the fish hasn't soaked for enough time, it'll be too salty and will ultimately ruin the dish. If soaked for too long, it's easier to remedy - just add salt to the dish. After the fish has been soaked, it is ready do be cooked, or frozen right away.
The higher pieces are ideal for cooking over the grill or in the oven. The medium ones are usually used for dishes where the fish is cooked in stews and the lower pieces are used for recipes where they are broken down into strands.
I hope this was a compreehensive explanation of one of Portugal's favourite fish.
