The French butter crisis is spreading.

On Wednesday evening, on her way home from work, Parisian Greta Morton popped into Carrefour, the ubiquitous French supermarket.

"I saw empty shelves in the cold section," Morton reports. "There really was no butter, except for a butter you find in plastic containers that no-one ever buys."

This sight is mirrored across France. A combination of low dairy production, and panic buying once the news got out, has left supermarket shelves literally bare across the country.

And if you think that doesn't amount to a national crisis, then I've got one word for you: croissants. French pastry requires a lot of butter to make.

The French are worried. According to Le Figaro newspaper, it's the worst butter shortage since the end of World War Two.

"It's the Chinese, they're buying all the butter," the Carrefour checkout guy told Morton (Chinese demand is part of the cause, but not the whole story).

Alison Meston, an Australian who has lived in France for some years, says the lack of butter is a "talking point" among her colleagues.

"There's lots of butter missing from the shelves in my supermarket," she said. "I could only buy the expensive salt crystal butter – which is fine by me because it's delicious."

It might not be a problem for hipster Parisians but it would be harder for "a family of 6 on the breadline if you're now paying 1.15 euros for your croissants when you were paying 90 cents", Meston said.

Morton also checked out "La Butte Fromagère" near Montmartre, a traditional cheese and dairy shop. It was well stocked.

Shop assistant Alexia told her the shortages were only in "industrially made butter – we sell artisan made butter and there's no shortage there".

Alexia told Morton the shortage was due to strong demand: "it's the Chinese, they're buying a lot… but don't worry Madame, you know when people say there's a shortage of something, everyone panics and goes and buys it all up."

According to European Commission statistics, the price of wholesale butter shot up from a low of €250 per 100kg in January 2016 to €650 in August this year.

Butter prices for consumers doubled.

Part of the cause is because demand is high.

Across the West butter is seeing a revival as new research casts doubt on the health risks of saturated fats. And buttery pastries are increasingly in vogue in Asia and the Middle East.

China butter imports from the EU rose by 19 per cent this year compared to 2016, though the EU's total butter exports in 2017 actually fell by a fifth.

It wasn't just butter. Chinese demand for EU cheese rose by 23 per cent, demand for skimmed milk powder by 29 per cent, and whole milk powder by 11 per cent.

But turbulence in Europe's butter market can really be traced back to the abolishing of milk quotas in 2015.

Brigit Busicchia of Macquarie University wrote for The Conversation that the liberalisation of the EU dairy market drove farm-gate prices down, so farmers across Europe scaled back production.

The recently strong euro also didn't help matters.

There was a 5 per cent slump in EU butter production this year compared to the year before, according to the latest official figures.

The latest forecasts suggest that a surge in production in the second half of 2017 is on its way to fixing the problem.

Bakers are worried. The Christmas cake season is imminent, and they all need butter. If supply doesn't return quickly enough, they're going to have to pass the cost on to customers.

France's agriculture minister told parliament on Tuesday that retailers and suppliers should agree on price adjustments in order to maintain deliveries, Reuters reported.

There is one thing everyone agrees on. No matter how bad things get, they're not going to substitute butter with margarine in the croissants.