Naples gave birth to the margherita, but now passions run high over the addition of stilton, port or even liquorice

Enzo Coccia has an evangelical air as he discusses his spring pizza – piled with asparagus, buffalo mozzarella, sheep's cheese, lard and beans. "They may say I am a heretic, but I just want to experiment," says the controversial exponent of the Italian trend for what are being dubbed gourmet, or "ultra-pizzas".

The fashion for ultra-pizzas has spread throughout Italy. But as Coccia is constantly being reminded, this is Naples, the home of the tomato and mozzarella margherita. Since opening in 2010, Coccia's restaurant, La Notizia, has whipped up an almighty row, provoking an army of growling traditionalists to voice their contempt for Coccia's daring combination of salt cod with mozzarella, his use of figs and pesto and his €25 truffle oil pizza. His innovative – some would say sacrilegious – approach has divided a city.

"There is no such thing as gourmet pizza, we are not OK with this," said Sergio Miccu, head of the Neapolitan Association of Pizza Makers, which has secured EU certification for the margherita and another Neapolitan standard, the tomato, garlic and oregano marinara.

"Pizza was born as a food for the poor and any complicated pizza loses its identity," he added. To prove his point, Miccu listed off the elements that make up the perfect – and now Brussels-patented – margherita: a 33cm diameter, 2-3cm high crust, San Marzano tomatoes, cow's milk mozzarella from the region of Campania and olive oil, all cooked in a wood oven after the dough has risen for nine hours.

But a growing number of pizzaioli, or pizza makers, up and down Italy, are pushing beyond that, taking their lead from a Rome restaurant, La Gatta Mangiona, which has tried out duck and asparagus and steamed chestnut and mushroom pizzas.

In a country that normally prizes simple ingredients and traditional recipes, pizzaioli are now attempting stilton and port pizzas as well as shrimp, saffron and liquorice pizzas.

For Coccia, the economic downturn means more chefs are colonising the poor man's food. "As the crisis makes people want to spend less on eating well, two-starred chefs I know are rushing to install wood-fired pizza ovens, while I am being considered a chef instead of just a pizzaiolo," he said.

What makes Coccia different is that he has dared to open for business in the town where pizza was first popularised and where in 1889 a pizzaiolo named his new mozzarella, tomato and basil pizza – mimicking the white, red and green of the Italian flag – after Margherita of Savoy.

Naples' staple got a further boost from the 1954 Italian comedy The Gold of Naples, where Sofia Loren plays a pizzaiola in the working-class district of Materdei. Five decades on, Starita, the local restaurant which kitted her out for the role, is still pulling in the crowds.

"I am dead against these gourmet pizzas – a pizza restaurant must be quick and cheap and turn out at least 400 pizzas a night," said Antonio Starita, 70, whose grandfather opened the restaurant in 1901.

"I have seen cream being used, and it doesn't get worse than that," he added, while pounding dough beneath the obligatory photos of the pope and former Napoli footballer Diego Maradona.

At Di Matteo on Via Dei Tribunali in the heart of Naples, where 600 pizzas are served a day and a margherita costs €3, the owner, Salvatore di Matteo, dismissed the ultra-pizza trend as "just like a cold, by which I mean it should pass".

"For me," he added, "gourmet means talking about what you eat."

A third of Di Matteo's business is folded and fried pizzas – typically stuffed with ricotta, provola cheese and cicoli, a local type of pancetta. For Neapolitans, he said, it is even more of a tradition than the margherita. "Fried pizza was bigger than oven-baked pizza in Naples until the 1950s. It needs good oil and a pizzaiolo who can tell the oil's temperature just by looking at it – it's such a hard technique that it hasn't caught on outside Naples," he said.

For food expert Davide Paolini, the new gourmet pizzas "can be great, but it's no longer pizza". He did, however, praise the work of the new wave of pizza chefs in perfecting the dough base. "Gourmet pizzaioli are doing serious research on flours and methods of raising the dough, particularly Enzo Coccia," he said.

While his ingredients may be raising eyebrows in Naples, Coccia's light, perfectly baked pizza bases – thanks to his fanatical attention to detail – are winning plaudits from his peers. After a long night's baking, he still has the energy to describe the perfect mix of humidity, volume and temperature for raising dough, before he sketches out the perfect proportions for a pizza oven on a napkin. "This hasn't changed much since the Greeks, but we are always looking to improve on things," he said.

At a second restaurant on the same street his menu is strictly traditional. As for the ingredients at his gourmet venture, some may be unorthodox but all are rigorously local.

"I did a fried pizza with mussels and pancetta based on my grandmother's skewers of mussels and pancetta, dipped in egg and breadcrumbs then fried," he said. "If I am innovating, it is only because I know the traditions."