How do taco trucks get their soft taco shells to have a slightly oily texture and more complex taste?

Question

When I get tacos from a taco truck or the more authentic Mexican restaurants here, the soft corn taco shells often have a somewhat oily texture and are a darker color than the shells are prior to being warmed/cooked. Here is one example and here is another example

How do they get the texture to be like that? I've tried using some oil when I warm the tacos in a pan, but that starts to make them crispy (the shells that I'm trying to replicate don't have burnt crispy spots) and the color doesn't get darker like trucks and restaurants manage. It also seems like the good chefs get the taco shells to have a more complex taste, whereas when I've tried it with oil or with no liquid, the shells aren't as tasty.

Answer 1

The oily texture is from the oil. The normal way to heat corn tortillas for tacos, to make them soft and foldable without weakening them, is to briefly heat them on an oiled flattop grill.

The darkness comes partially from having oil on them, and partially from the type of corn used. They do not significantly darken while being heated. If you go to a Mexican grocery store you'll see various shades available; supermarkets with a limited selection of Mexican ingredients will probably just have the common light-colored corn tortillas.

If you've tried frying them and they've become crispy or gotten burnt spots, you're probably doing them too long or at too high a heat (presumably in an attempt to darken them). You shouldn't try to cook them at this step: once they're warmed, they're done.