Kevin at Bacon Press, who's done fantastic work over the years researching the origins of other local traditions (the hofbrau, for example), traced Dutch crunch as far as the 1960s, when the now-defunct Parisian Bakery may have introduced it to San Francisco.
Whatever its origins, the bread is widely available. Dozens of sandwich shops still use it: Potrero's Calabria Bros., Roxie Market and Deli in the Inner Sunset, the Monterey Deli in Glen Park/Sunnyside, just to name a few.
You can't find Dutch crunch at any of the tonier markets or European bakeries, but I picked up rolls at Safeway (more like Dutch spotting, and not that great). Bacon Press prefers the rolls from Italian French Baking Company (1501 Grant). Tipped off by a Chowhound post, I also found rolls at Royal Bakery, a minuscule bakery at 4773 Mission St. in the Excelsior that sells telera and bolillos in addition to its biscotti, panettone, and Dutch crunch. Royal Bakery's crunch layer (produced by a sweetened rice-flour paste slathered over the dough) is more crumbly than most, but the roll made a good cheese-and-tomato sandwich.
When I told Malgieri about my purchase, he laughed: "A San Francisco Dutch bread from an Italian-Mexican bakery? That's great!"
As part of Malgieri's BAKE! tour, he's teaching a class at the Union Square Sur La Table on Saturday, Nov. 20, at 2 p.m. There appear to be spaces left. Go bring him a loaf of your favorite San Francisco Dutch crunch, and maybe he'll sign it for you.