Long before there were McNuggets, there were bolinhos de bacalhau, or fish balls; bite-sized quenelles of salt cod mixed with mashed potato that are Lisbon’s answer to fast food. Eaten hot or cold, as a mid-day snack or evening appetizer, they’re ubiquitous. And delicious. They also go great with a beer. The logic behind it is unimpeachable, too. A high-protein, low-fat snack or a trough of deep-fried McParts? No wonder the people here are all so trim. The secret to the bod must be in the cod.