Porto’s iconic, belly-buster sandwich is the francesinha. The clue is in the name, literally “little Frenchie”. In the 1950s and 60s, António Salazar’s harsh, myopic dictatorship turned millions of Portuguese into migrants: by 1970 – when the population of Lisbon numbered barely 800,000 – at least 700,000 of them were living in France. As well as money, the migrants sent home elements of French culture, and Portuenses took the croque monsieur to their hearts.

But as with most diasporic remittances, the classic French toastie was adapted, and the meagre croque became the francesinha – no longer a moderate-sized snack, but big and strong, a force to be reckoned with.

Double French … a francesinha and french fries at the Cantarinha Café. Photograph: Kevin Gould

Anyone aiming to polish off even half of one of these needs to be pretty forceful, for this little Frenchie is a tower of power. A doorstep sandwich layered with pork, then smoked sausage, then bacon, and topped off with a medium-rare beefsteak, it is finished with a fried egg and covered in a thick coat of cheesy sauce. It is heated through and then drenched in a murky dark sauce. A mountain of french fries is served on the side. Health food it’s not.

For lunch, or when hungover after a night out on this excellent town, try the award-winning francesinhas at determinedly un-chic A Cantarinha Café (Largo da Maternidade 75). After dark, daughter and father-run Bufete Fase (Rua Santa Caterina 1147) will fill any munchie-sized hole.

Francesinhas generally cost around €6.50, though many Porto bars and cafes offer two-for-one deals during happy hour.