The Porto francesinha - the drunk food that you eat when sober or hungover and can't actually get (because all the places are closed) when you are drunk (assuming you aren't drunk really early in the evening). Everyone recommends eating it, and there's a few names that come up as options. Some places are known to be cheap, our tour guide said anything really cheap is probably something you don't want to be eating.
The most famous venue is definitely Cafe Santiago (https://eatlikeushi.posthaven.com/cafe-santiago-porto-10-2013) and although I don't remember the experience that clearly, I do remember feeling wow this is heavy, thick and excessive and probably enough to try once in a lifetime. It seems lifetimes come around more often, and so wanting to try it again, I avoided the curiosity to relive the experience at Santiago and went to a local friend's recommendation of Brasao Aliados instead.
It's a much finer venue for one, more like a bar restaurant than Santiago's fastfood diner. The thing that also brought me here was the vegetarian option, which is hard to find out information about online.
- Francesinha with egg €10.5 - medium rare steak, bacon, chorizo, cheese, meaty tomato sauce, egg. Strong meaty flavours and quite salty, but at least the ingredients seemed decent quality (particularly the steak);
- Vegetable francesinha €10 - asparagus, mushroom, eggplant, fake sausage, tomato rich sauce. Less heavy and more tomato flavour but still a good alternative;
- Orange & mustard salad €3.5 - simple.
Finished with a large glass of white wine sangria 0.4L for €6. I would actually come back to this popular place for food and drink. That occasion would only be on the rare occasion of visiting Porto, so it probably would be to relive the francesinha.