My wife, who is French, mentioned that my in-laws, still unaware of the growing worries about butter scarcity, had been puzzled by her grandfather’s insistence that they stock up.

Of course, those in the industry — dairy farmers, butter producers, pastry makers — had been tracking the rising butter prices and growing tensions between producers and retailers for months. They knew what was coming, and told me so when I started making calls.

Annabelle Cantin, the head of marketing and communications at La Trinitaine, a food company in Brittany that makes buttery treats, told me that consumers and the media were only noticing now because of empty shelves in supermarkets.

“From a professional standpoint,” she said, “it has been visible for much longer.”

The Federation of Bakery Companies, another industry organization I reached out to, had even put out a statement in May, warning that “many companies will be struggling in the coming months, amidst relative indifference.”

I also recruited the help of our intern in the Paris bureau, Eloise Stark, who went to bakeries and supermarkets in Paris to see what shoppers and pastry makers had to say. One bakery told her that it had slightly increased prices, but only on the more fancy butter-based pastries, not on the sacrosanct croissant.

To get a better understanding of butter’s place in French culture and cooking, I reached out to Jean-Robert Pitte, a geographer and gastronomy specialist at the Sorbonne. He explained that France had long been divided in half, between a butter-using north and an olive oil-consuming south.

I later got confirmation from an impeccable source: my 89-year-old French grandmother, a Parisian whose family is originally from northern France but who married a southerner from the Hautes-Alpes region, where olive oil is more prominent.