A delicacy for medieval monarchs, a plate for the poorest and a treat for Tito, animal testicles, with a pinch of humour, are back on the menu, at least at one Serbian food festival.

A visitor needs no road signs to reach the tiny central village of Lunjevica, population 500. They can follow the smoke and smells from the barbecues and kettles at the 10th unofficial testicle-cooking "world championship".

"In our region, we have cooked testicles for ages: our fathers prepared them, our grandfathers before them," local farmer Dragan Todorovic said, slicing a set of horse testicles.

The challenge for this year's 20-some competitors was to make the best "balls-goulash", a twist on the ubiquitous regional stew but replacing classic meat cuts with testicles from rams, calves, bulls, donkeys, horses or other animals.

Some say the testicles should be diced into tiny pieces and soaked in wine for at least 30 minutes for the right consistency before simmered with the onions, garlic, peppers, tomatoes and herbs.

"Beware. They should be cut diagonally, otherwise they lose their aphrodisiac effect," warned Zdravko Djuric, a competitor from northern Serbia.

Local lore considers testicles an aphrodisiac, given their naturally high testosterone level, and organisers tap into this reputation.

"Better for the libido than any Viagra," reads one of the slogans for the festival, which draws up to a thousand people, many from abroad.

"It's so totally crazy, I had to be here," said German cook Andre Niediek, a chef in a Cologne restaurant, stirring a pot of bull testicles spiced with "fine Serbian paprika".

His own secret is timing. "Two and a half hours at least. This is not a quick lunch or fast food meal. "

Some come "out of curiosity", like Zoran Jeftic from the capital Belgrade who found the stewed glands "tasted similar to chicken."

The festival's founder Ljubomir Erovic says the event is not only a culinary competition but a bid to sweep away prejudice against Serbia that dates back to the 1990s wars in the Balkans. So he injects lots of humour, starting with the official poster -- a drawing of a pot-bellied, mustachioed chef with his own testicles drooping right into his boiling cauldron of stew.

"The French boast with the Tour de France, and we boast with balls," joked farmer Todorovic.

Erovic, who has authored a book entitled "Cooking with Balls", said the delicacy was a favourite with many past notables, including Serbia's 19th-century ruler prince Milos and communist Yugoslavia's strongman Josip Broz Tito.

The four-member jury includes an American, Boston filmmaker Anna Wexler, its sole woman and non-Serb who discovered the festival "googling weird things late at night".

When she contacted Erovic, he invited her to the event where she has been a regular since 2009. "Every year I come all the way out here just to judge the balls," she said laughing.

A ram's testicles stew was this year's winner, but all entries were sampled at gala dinner where cocktail nibbles were grilled lamb testicles rustled up by a Danish competitor.

An annual tongue-in-cheek prize is also awarded to the "person with the biggest balls", which this year pits German Chancellor Angela Merkel against US intelligence leaker Edward Snowden. Voting goes through the end of the year on the festival's website.

Among previous winners were US President Barack Obama in 2010 and Wikileaks founder Julian Assange in 2011.