Not many great ideas come off the back of a hangover, but this was one of them.
The little cafe in Lisbon we were sat in had proudly declared in the window "temos caraóis" ("we have snails"). But we had just ordered another Portuguese delicacy — the francesinha.
Perhaps you yourself have been acquainted with the franceshina — in a recurring nightmare, or on a city break to Porto. But for those unacquainted with it, this Portuguese gut-buster is half sandwich, half lasagna, and — for those who laugh in the face of maths — half beast.
It's the kind of sandwich where you're not sure whether the waiter is bringing it out, or it's bringing out the waiter.
It's the kind of sandwich that Elvis would have done a double-take at, shaken his be-quiffed head and mumbled, "no thankyouverymuch."
It's the kind of sandwich that — because of its human head sized proportions — the olive on a toothpick sticking out the top, makes you genuinely concerned that if you round off the meal with it, you might burst, Mr Creosote style, over the restaurant walls.
Based on the blueprints of a small house, its walls of white bread encase an inner brickwork of ham and chorizo sausage. The floor is made out of steak. The outside walls are slathered in a cheesy, bechamel grouting, and it has been fitted with a fried egg roof.
For good measure, the entire structure sits in a moat of spicy beer sauce.
It invariably comes served with a garden of French fries.
Back in Lisbon, the subsequent carb and protein-induced stupor we found ourselves in was such, that we quickly began to think that perhaps we'd dreamed up the francesinha all along.
Nonetheless, the memory of it has been haunting us ever since — and now, returned to London, we can only calm our nerves by tracking down this ingenious, terrifying slab of meaty Brutalism.
"If anywhere's going to have the francesinha, it's Stockwell," we decide — and begin to scour the menus of all Little Portugal's top eateries. Stockwell is not too far from where we live, meaning we can waddle home, or at least get an Uber back, in time to die peacefully in our beds.
But this francesinha hunting isn't as easy as you might think. One of the best-known Portuguese canteens does do the francesinha, but, according to online reviews it's got frankfurter sausage in it, and isn't very good. "That's like going to see Queen post Freddie Mercury," we concur, "Pointless."
Elsewhere, we struggle to find a Stockwell francesinha at all. Perhaps it's one of those things that's off-menu, like the inexplicably off-menu burger at Joe Allen. Yes, that must be it. And with that thought in our heads, we go to one of the area's best-loved Portuguese eateries, A Toca. Immediately, things are looking up — the hustle and bustle of tapas plates shuttled across the room; the roar the clink of Super Bock bottle on Super Bock bottle; some football teams we've never heard of, playing in the background.
We flick through the menu — it's the same as the online version — no francesinha. But of course, we know better than that. We've got the codeword.
"Do you do francesinha?"
We sump back into our chairs. "Tapas then?" "Tapas."
Each mouthful of clam and pork belly is utterly delicious, but there is no getting over the fact it is not francesinha. We have not given up the fight, but we must now rest awhile. The francesinha, we have discovered, is the Moby Dick of the sandwich world.
On the weekend, we are in a north London pub garden, working up a hunger after Open House and a few pints of craft beer. "What do you fancy for dinner? Indian? Chinese?"
"Francesinha?" The second half of the word inflecting upwards in uncontrollable excitement.
The hunt is back on. We race to our phones, and discover a place in Camden called FRHappy, which not only serves, but specialises in the Francesinha. A dedicated 'francesinha' page explains:
The most consensual story about the origin and invention of the Francesinha relates to a returned emigrant from France and Belgium, Daniel da Silva. In 1953 when returning to Porto, Mr. Da Silva decided to completely change the French traditional "croque-monsieur", adding layers of different types of meat and cheese as well as a secret and spicy sauce on top of the sandwich.
So on top of everything else, the francesinha is a middle finger — a middle finger dripping in bechamel, mind — in the face of French cuisine? It just gets better and better.
Before we've finish swotting up , we're ringing up FRHappy to book a table. But they're not answering. They're not bloody answering. And then we see the grim expression on our friend's face.
He nods like a doctor would when delivering the news of the death of a loved one. "Permanently."
But we fight through the grief. Nothing is going to stop us now. We've had four pints. We get back to searching, and eventually pull up Bar & Co Cafe — Google has slurped up an image from a reviewer... it's of a francesinha.
Before we've finish looking at the picture, we're on the Northern line.
Bar & Co Cafe — just round the corner from Camden's Brewdog — is like a lo-fi version of A Toca. It's a smaller, bar-like affair, where numerous Portuguese football matches play out on screens (again), and the friendly hum is punctuated by the occasional roar of jubilance (again).
Our eyes, however, are not on the football, but the menu:
It is, perhaps, the longest 15 minutes known to man. But eventually, the beast is brought to our table. We have asked for the spicy version — which seems to be a normal francesinha, sprinkled with chilli flakes — like this thing really needed another ingredient.
It is difficult to explain the ecstasy of each mouthful — but it's a bit like breathing in lungful after lungful of juicy, meaty, creamy, cheesy, spicy, tomatoey air.
Three minutes later, as we polish off the last of the sauce — carefully licking it from the serrated steak knife (and pilfering the leftovers of the friend sat next to us) — we know that we have finally found peace.
For a few seconds, anyway. Because then we realise what we must now do.
We must hunt down every francesinha in London. We must destroy ever francesinha in London. We shall not rest until every francesinha is eaten for good. We must rid of ourselves once and for all of this delicious, delicious bastard.
Have you encountered the francesinha? Where's your favourite place to eat it in London? Let us know in the comments (please finish eating first — even typing a few words after a francesinha could give you serious indigestion).