London, England (CNN) — They meat at dawn.
That's not a typo.
With a side order of fast cars.
Vintage London market and pub
The venue is Smithfield Market, a beautiful Victorian structure in east London that slumbers during daylight but comes alive at 2 a.m. to accommodate a frenzy of pork, beef, lamb and poultry sales.
CNN invited the chefs to cook a dish for its Culinary Journeys series and on the menu is a simple favorite from Henderson's arsenal of classics: roasted bone marrow on toast, with a parsley salad.
First ingredient is an early start, so we meet in The Hope (94 Cowcross St.; +44 20 7253 8525), a vintage London pub that opens early to cater to the all-night traders.
Dressed in his trademark battered blue jacket and owlish spectacles, Henderson doesn't stand on ceremony.
Fresh off a plane from New York, he's tucking into his second Guinness when Bottura turns up, characteristically wired, but still hunting for a decent jolt of espresso.
Dutch courage isn't a bad idea before tackling Smithfield, where white-coated butchers and traders have little time for the uninitiated.
"They don't welcome you in," says Henderson "It's a closed world."
At times we have to dive for cover as carcasses are slung on shoulders and carried through the architectural splendor of the market's lofty hallways.
It's a sight worth seeing though.
As the last of London's great central food markets, Smithfield is a meaty piece of history that sits on prime real estate, attracting regular approaches from hungry developers.
Meat has been traded at Smithfield for hundreds of years.
The current structure was built in 1868, complete with its own underground railway, to replace an open site where blood from slaughtered beasts washed through the streets.
The entrance to its underground parking lot doubled for MI6's emergency operation base after its HQ was destroyed in "Skyfall," the most recent James Bond movie.
There are guided tours once a month -- perhaps a better option for the non-meat-buying visitors -- but since we're on a meat-buying mission, we dive straight in.
After sneaking a look in some of the meat fridges, Henderson and Bottura hand over £5 ($7.60) for a bag of calf marrow bones.
Then it's back to St. John (26 St. John St., London; +44 20 7251 0848) the restaurant Henderson co-founded 20 years ago with Trevor Gulliver, creating a menu based on the principle, radical back then, of "nose-to-tail dining" that uses every part of the animal. Coincidentally, it opened at the same time Bottura was launching Osteria Francescana (Via Stella, 22, Modena, Italy; +39 059 223912), his Michelin-starred restaurant in Modena, Italy, with a menu that followed similar guidelines.
Over the years, the chefs have sought each other's company, drawn by shared beliefs on making the most of previously unwanted ingredients.
'Godfather of meat'
"It's self-explanatory," says Henderson. "It's working your way from one end of the animal to the next. That decides your menu.
"It's only polite, once you've killed it, you eat it."
Bottura agrees, hailing Henderson as the "godfather of meat."
"It's a very deep idea not to throw away anything. Respect the animals from nose to tail.
"Go simple, stay simple, keep it simple. It's always the best thing."
At this time of the morning St. John's is devoid of diners but alive with activity.
The scent of fresh loaves from St. John's own bakery waft through the white-walled semi-industrial space (converted from an old smoke house) as chefs arrive to prep for lunch.
A few customers drop by to buy bread or cakes to take away -- St. John's prides itself on being a community restaurant serving the neighborhood that has gentrified around it over the past two decades.
In the kitchen, head chef Chris Gillard takes over preparing our dish; Henderson has bowed out of his role as chef due to the onset of Parkinson's disease and Bottura is wary of invading another chef's territory.
The bones are placed in a roasting dish and into an oven for 20 minutes at 190 C (275 F) until the marrow starts to loosen but not melt.
When ready, it's plated with toast and a salad of chopped flat parsley, fine sliced shallots and capers -- all dressed in lemon juice and extra virgin olive oil.
The glutinous marrow is spooned from the bones onto the toast (Henderson recommends using the handle of a fork), then covered with the salad, sea salt and pepper.
Against all appearances, it's delicious.
Even more so when finessed with a gift from Bottura, a 25-year-old balsamic vinegar all the way from Modena.
"Sparkle of creativity"
The marrow dish isn't Bottura's only contribution to the day's menu.
In between talking excitedly about the London art and music scene that inspires him -- and an impromptu haircut -- the mercurial Italian chef hits his cell phone to summon another Modena specialty.
The luxury Italian car, on loan from the Italian manufacturer's UK operation, pulls up outside St. John as guests are arriving for lunch.
Bottura excitedly gets behind the wheel and revs the V6 twin turbo engine until it sings so loudly that a film shoot next door (reputedly starring Michael Caine) probably had to halt production.
Before treating Henderson to a spin around London -- and pulling up so close to a metal post that the $140,000 Maserati's minders visibly wince -- Bottura reflects on his culinary journey to the city.
"For me it's very important to travel like this, in places like London, full of culture," he says.
"I live in a small town, Modena, that is, incredibly, known all over the world for fast cars like Ferrari, Maserati, but also for slow food.
"When you get an explosion of cultures, a mixture of cultures as you have here --- you walk on the street you get all these languages and cultures and smell all this kebab, Italian, pizza, burger, pub, beer, everything compressed in 20 meters -- it's amazing.
"You have to absorb this kind of feeling, these kind of flavors and bring it back, make it yours.
"Because through the sparkle of the these meetings, of this culture, there is a new sparkle of creativity."