Tacos al vapor, "steamed" tacos, are another name given to the tacos de canasta sold by street vendors from a cloth-draped "basket." Tacos de canasta are filled in advance, folded in two — they tend to be slim — and fitted, with several hundred of their fellows, into a basket that is carried to the vendor's place(s) of business. Their collective warmth has also prompted the name tacos sudados, since the texture of the tortillas is consequently "sweaty."
By contrast, at Las Conchitas — which functions more as a restaurant than as a bakery — the tacos al vapor never see the inside of a basket. Fillings of cabeza de res and lengua (beef head and beef tongue, $2.50 each) await at a windowside steamer, and tortillas for each order are warmed directly atop the meats. The assembled tacos al vapor don't have time to develop the enticing juice-soaked texture of some tacos de canasta, true, but the tortillas are soft and warm, the fillings, ample for the price.
H/T Ike Hull (via private communication)
Las Conchitas Bakery
48-11 Fifth Ave. (48th-49th Sts.), Sunset Park, Brooklyn
Tacos al vapor available Monday through Saturday after 3:00