The 1940s Cake Accident That Ultimately Became A San Francisco Legend

Experimental home cooks know that, sometimes, kitchen mishaps can lead to unexpectedly scrumptious destinations — like the creation of St. Louis' iconic, gooey butter cake. Today, we're taking a closer look at another confectionery-mistake-turned-marvel: Blum's coffee crunch cake. The dessert was invented at the eponymous Blum's Bakery in San Francisco in the 1940s after an unintentional candy-meets-cake baking accident, and remained a beloved regional classic until Blum's closed in the 1970s.

Coffee crunch cake began as the innovative rescue mission of master baker and Le Cordon Blue-trained pastry chef Ernest Weil. Per the lore, after a bakery employee accidentally overboiled a batch of Blum's (supposed-to-be) soft coffee candy, Weil leapt into a thrifty effort not to waste it. The pastry chef broke the crispy, honeycombed sugar candy into small pieces and added it to Blum's regular sponge cake. The result was a light, fluffy, lemon-tinged chiffon cake dotted with crunchy textural morsels. Over time, the West Coast classic was refined into a dimensional, decadent, two-layer treat covered in bittersweet frosting. To assemble, the chiffon cake gets allover-frosted in a coffee-flavored whipped cream infused with vanilla and instant coffee granules, and sprinkled with a generous coating of the shattered coffee candy pieces. A center layer of candy shards (a combination of sugar, strongly-brewed coffee, corn syrup) gives this cake the "coffee crunch" factor in its name, and it quickly emerged as a signature sweet of the city.

Blum's Bakery was established in 1892 on Sutter and Polk. The bakery moved to its longtime Union Square location on Polk and California in 1907, where the crumb cake would be invented. The move was prompted by the infamous San Francisco earthquake of 1906, which was followed by a massive citywide fire that lasted for four days, destroying the first bakery. But, in another bizarre incidence of "mistakes becoming unexpectedly good results," Blum's coffee crunch cake found a fast fanbase among the patrons of the Union Square area — an upscale clientele dressed in 1940s-60s finery (think hats and gloves) to shop the surrounding stores. Although, then and now, coffee crunch cake and the "Blum's" name are held close to the hearts of San Franciscans citywide.

The treat remained ultra-popular until 1972, when all Blum's stores (including the flagship Union Square San Francisco bakery) closed their doors. Still, for San Franciscans, the cake's legacy lives on. In 2017, local San Franciscan news outlet Nob Hill Gazette reported that Blum's coffee crunch cake was being sold at Yasukochi's Sweet Stop, located inside Super Mira Market in Japantown. Per the outlet, the Yasukochi's team was taught the recipe by a former Blum's employee after the bakeries closed in the '70s. For foodies beyond the West Coast, Tasting Table has gotten our hands on Blum's official coffee crunch cake recipe for a taste of the real deal.