Wikipedia: Avocado toast
Avocado toast is a type of open sandwich consisting of toast with mashed avocado, and any of a variety of spices and flavorful ingredients. The most popular are usually salt and black pepper, sometimes lemon juice or other citrus, while others include olive oil, hummus, vinegar, red pepper flakes, feta, duqqa and tomato.
 
Avocado toast became a food trend of the 2010s. It has appeared on café menus since at least the 1990s. Following avocado toast’s elevation to trend status, the act of ordering avocado toast at a café was criticized as a symbol of frivolous spending.
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In the San Francisco Bay Area, people have been eating avocado toast since at least 1885. In 1915, the California Avocado Association described serving small squares of avocado toast as an appetizer. In an article published in The New Yorker on 1 May 1937, titled “Avocado, or the Future of Eating”, the writer eats “avocado sandwich on whole wheat and a lime rickey.” In 1962, an article in The New York Times showcased a “special” way to serve avocado as the filling of a toasted sandwich. According to The Washington Post, chef Bill Granger may have been the first person to put avocado toast on a modern café menu in 1993 in Sydney, although the dish is documented in Brisbane, Australia, as early as 1929. In 1999, food writer Nigel Slater published a recipe for an avocado “bruschetta” in The Guardian. The journalist and editor Lauren Oyler credited Cafe Gitane with bringing the dish to the United States in its “Instagrammable” form, as it grew as a food trend.
       
Wikipedia: Bill Granger
William Granger OAM (29 August 1969 – 25 December 2023) was an Australian self-taught cook, restaurateur and food writer. Based in Australia and London, he worked internationally.
 
Australian Food Timeline
1929 Avocado on toast first mentioned
In an article in The Telegraph, Brisbane, in 1929, Margaret Cullen wrote about Robert Walsh’s Redcliffe garden where avocados were among the tropical and sub-tropical fruits being grown. She described the fruit, explained its history (omitting to say that the Aztec word for avocado, ahuacatl, also means “testicle”), and wrote that: ‘They are superb served as a salad (with or without other raw ingredients), with a mayonnaise dressing. Spread on toast or water biscuits and lightly peppered and salted they make a delicious “savoury.”’ Her article is likely the earliest mention of avocado on toast.
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The credit for introducing avocado as a breakfast dish probably goes to Bill Granger of the eponymous bill’s,  who put it on the morning menu in his Sydney restaurant in 1993. He was the first of many, and avocado with feta, or goat’s cheese, or tomatoes, or a poached egg, or bacon, or all of the above became a standard café breakfast dish. Then, in 2017, demographer Bernard Salt caused a furore by blaming a liking for a pricey smashed avocado on toast at a café for the millennial generation’s failure to accumulate a house deposit.
     
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Suzanne Xie
@suzannexie
i am really going to miss café gitane…their avocado toast and watermelon juice!
11:45 AM · Jul 22, 2008
   
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Andrew Renton
@andrewrenton
Avocado toast at Café Gitane.
2:41 PM · Aug 14, 2009
   
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Andrew Renton
@andrewrenton
Avocado Toast and Watermelon juice at Gitane. Lower East Side vintage shopping.
2:17 PM · Aug 23, 2009
   
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ajua bliss
@juasnua
@ Rubys on mulberry. About to murk this avocado toast!
10:18 AM · Jan 9, 2011
             
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wit & whimsy
@meghandono
Brunch at one of Gwyneth Paltrow’s favorites, Granger & Co- avocado toast of life! #bolohopsthepond @… http://instagram.com/p/qG54QXlB6a/
7:26 AM · Jul 6, 2014