Bacalhau
Bacalhau is a type of dried fish that has a specific place in Portuguese cuisine. The fish is taken in Norwegian Sea waters, then sliced, salted, and dried. Norway and Iceland are Portugal's primary suppliers. Portugal is the world's largest consumer. This dish was a true nutritional breakthrough. People established an extraordinarily extended shelf life by drying and salting fish, allowing them to be transported from fishing sites to Portugal (which took up to 3 months).
Similarly, even the same food can be prepared very differently in different parts of the country. Fresh or fresh-frozen cod does not have the same flavor as Bacalhau. As a result, substituting frozen cod for the ingredients will result in a completely different dish. This is one of the most traditional Portuguese dishes that you should not miss while visiting Portugal.