It is perhaps unfair of me to fault Mother Flipper for slightly overcooking their burgers, missing by less than a minute the liftoff from the flat-top griddle to juicy medium rare. This has happened twice, first in February at its original home ground at Brockley Market in Southeast London and again yesterday at its Eat Street debut behind Kings Cross Station.

In the US you wouldn’t expect short order cooks at diners, truck stops and burger stands to make the distinction between pale and deep pink, especially burgers below the 5-ounce and 4-dollar barriers. So why hold their UK counterparts to a higher standard?

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I could answer my own question by noting that Mother Flipper asks £5 for its cheeseburger, roughly 8 dollars. But prices for satisfactory beef and authentic plastic cheese are higher here. Good cheap burgers (with this notable exception) don’t really exist in London. Comparing US and UK burgers according to price is problematic.

To learn the reason why I make such a big deal about seven small degrees, estimating internal meat temperatures from 55-degree (Celsius) for medium-rare to 62-degrees for medium, you have to inspect the pavement.

I tried two Mother Flipper cheeseburgers yesterday. The first, cooked a notch above medium though I asked for medium-rare, was nicely constructed with beautiful ketchup/mustard art on the bun, very tasty and, importantly, a safe object to hold in my hands. No leaks. I didn’t embarrass myself. But the second, cooked as ordered, was a thing of danger and looming dry cleaning bills, bleeding beefy juices from every pore of its patty.  Unable to wait to find a place to sit I devoured it walking away from the stall, leaving a trail of grease and mourning every lost drip.

A street food favourite in the heart of the West End, Yang Guang stuffs each bun with a plump little patty of minced and marinated pork, its juices easily absorbed by the piping-hot fluff all around it. As viewed in the photo at the top of this post I’ve squirted the pork not with ketchup but with Sriacha hot sauce.

Importantly, the meat filling, hand-shaped into one solid piece, is not mealy, mushy, strippy, chunky, BBQy, cabbage-y or sweet as it can be with other baozi. Sure enough there’s a burger in that bun – a fresh, moist, tasty, £1.70 Chinese pork burger.

see The Best £2.10 Pizza Slice in London

London is the beneficiary of O’Sullivan’s good timing. After living and eating in Korea for two years he and partner Sarah Hogg, who’s from Scottish Borders, have rolled out their street cart just as sliders and Korean everything have emerged as want foods. They’re serving two different Korean-styled sliders (£2.50 each, £4 for a pair): lively but non-lethal kimchi with bacon and Korean-marinated pulled pork with crunchy sesame ginger cole slaw. O’Sullivan heats the prepared kimchi and pulled pork on his flat-top griddle. I tried both sliders and liked them enough to request a third – a mix-and-match pairing of kimchi and pulled pork.

Would I sulk if O’Sullivan eventually replaced the bacon with tender pork belly and crisp crackling? Think not. Would I lose sleep if his pulled pork got drippier over time? Duh! But for now, the only component that demands an emergency rethink is the drab, bready Sainsbury’s bun. It would help to toast or steam it on the griddle so that the slider felt warm and inviting as you transferred it from hand to mouth. But what’s really required is improved packaging with the character to complement the kimchi and coleslaw.

O’Sullivan and Hogg may be seeking a new home for their street cart following their royal wedding weekend gig at the Real Street Food Festival (Southbank Centre). You can track their movements on the Street Foodie website. But first their Korean sliders merit a new housing.

Last night’s communication breakdown between Yianni and myself at The Boaters Inn in Kingston was less about our respective Englishes than the shading of our burger language. I understood “medium rare” to mean pink. He took my order of “medium rare” to mean he should cook it longer than he thought desirable.

The burger was great, I told him afterwards, “but could have been pinker and juicier”.

“What did you expect?” he replied, not believing I could be the burgermonday dude he’d heard about. “You ordered it medium rare!”

Rare, the default level at this pub-roving burger trailer and twitter phenomenon, is not so much red as very juicy. The Meatwagon’s medium-rare is merely juicy. The utter joy of very became obvious to me when I tried a second burger, this one ordered without mention of the dreaded M word. (When you catch up with The Meatwagon at one of its host pubs I’d suggest you not even wear a medium t-shirt for fear of a mixup.)

Yanni wants no part of the gourmet burger trade. Unlike Goodman, The Gun or  Hawksmoor he was not influenced by the New York School of Steak Burgers. His is a burger-joint burger, the speciality of American diners, drive-ins and lunch counters.

He flattens soft balls of mince by hand on the blistering griddle – no two Meatwagon burgers are exactly alike! – and only then does he season them, liberally, with salt and pepper. The burger sizzles on the griddle, encrusting both sides as the fatty juices leak from the deliberately crumbly periphery. Later Yanni squirts water on the griddle and places a metal dome over the burger to steam it. Quickly it is time to bun the burger and bed it with ketchup, mustard and dill pickle (American gherkin).

Yanni rotates an assortment of burger toppings and variations but doesn’t really get the meaning of a burger without cheese. “They all have cheese” he tells the woman taking orders and managing the queue. Guess it doesn’t matter if he doesn’t speak or think in Greek that much anymore: Once a cheezborger chap, always a cheezborger chap.

To find out where Yanni’s Meatwagon will be next, click here or follow him on twitter @themeatwagonuk.