Crispy potato and chorizo is a classic taco combination, but as much as I love it, it's usually one of the last options I'll pick at the taqueria. The truth of the matter is, it's pretty much impossible to start with raw chorizo and deliver a perfect chorizo taco within the few minutes that a taco truck will allot per order. At least if you like them the way I do.
The ideal potato and chorizo taco should be deeply browned and flavorful, each crisp cube of potato coated in a thin layer of bright red fat packed with spicy, meaty flavor. The chorizo itself should have a range of textures from tender and moist to crisp. It's a very straightforward process to get there, but it does take a bit of time. Here's how I do it.
Let's get one thing straight right off the bat here, closely followed by a second, equally important thing. First, when we're talking chorizo tacos, we're talking Mexican chorizo. Where Spanish chorizo is a firm, raw, dry-cured sausage flavored with smoked paprika and South American chorizos tend to be coarse ground garlicky sausages cooked in their natural casings, Mexican chorizo is that loosely bound, finely ground, by-the-pound, best when browned stuff that you'll find in the fresh sausages department. It comes stuffed either into natural casings, or, more often than not, into plastic sleeves that need to be sliced and squeezed out before cooking (I have a friend who once tried to cook Mexican chorizo on a grill, plastic sleeve and all. Don't be that guy.)
Mexican chorizo is highly seasoned with warm spices like cinnamon, cloves, and coriander, bright red from a combination of paprika and achiote, and tangy from vinegar. Because it does not need to be aged or cured, it's one of the easiest sausages to make at home. These characteristics also make it an ideal sausage for producing a fully vegan version (indeed, this is one case where I prefer the vegan-ified version to any store-bought pork version).
The real key with cooking chorizo? Cook it until you think it's done, then cook it some more. And some more. And still more. Nope, not quite done yet, keep going.
When just cooked through, chorizo has a saucy, almost Bolognese-like consistency that works if you're using it as a pasta sauce or a topping for a hot dog or hamburger, but in a taco, you want a bit more textural contrast.
By cooking the chorizo way past the point where you think it's ready, you slowly reduce the liquid that the pork expresses. As the liquid evaporates, the flavorful fat that was initially locked into a creamy, stable emulsion will break out. This is a good thing, and if you listen carefully, you should hear a distinct difference in the noise coming from the pan.
What was once a wet, sputtering, pft pft pft sound will transition into a sizzling, crackling sound—ssSSSssszzzzzKRAKzzzzzsssss—as your liquid transitions from being mostly water to mostly fat.
It's only once this transition occurs that the temperature in your pan can start getting into the serious browning range, above around 350°F or so where the Maillard reaction begins to take place in earnest, adding layers of flavor to your chorizo and giving it that wonderful crisp-moist texture (and don't be afraid to add a little extra fat to the pan in the form of vegetable oil, lard, or shortening if your chorizo is not quite fatty enough to get a really good sizzle going).
Cooking out the moisture in chorizo is doubly important if you're going to be combining it with potatoes. Without excess water content, your potatoes stay crisp even after folding them into the cooked chorizo, and that flavorful oil that has broken out of the sausage coats each piece of potato with more flavor than you could get with a watered down version.
Just as with my technique for the best potato hash, the real key to the crispest potatoes is to par-boil them in water with a touch of salt and vinegar added to it. Par-boiling the potatoes gelatinizes the outer layers of starch, which then dehydrate and crisp up when you subsequently fry the potatoes in hot fat. This delivers a far thicker, crisper crust on your potatoes than simply frying raw potatoes ever could.
The vinegar, on the other hand, lowers the pH of the water. Pectin, the carbohydrate-based glue that holds vegetable cells together is much harder to break down in lower pH environments, which means that while your starch is gelatinizing, your potatoes will maintain their shape without running the risk of breaking down or collapsing.
Once my potatoes are par-cooked, I fry them in a cast iron skillet with a bit of vegetable fat, tossing them and stirring them slowly so that they get a chance to build up a nice, even, crisp golden brown crust. You'll know they're ready because you'll be struck with an irresistible urge to start picking them out of the pan, fingertip burns be damned.
Once both the potatoes and the chorizo are crisp, it's a simple matter of putting them together...
...then stuffing them into hot, lightly charred corn tortillas.
Simple tacos with amazingly delicious fillings like this need nothing more than a bit of fresh diced white onion and cilantro for crunch and the tiniest drizzle of salsa verde and lime juice for brightness and heat.