The menu included guacamole, chili con queso, roasted corn, tres leches, a flourless Mexican chocolate cake (two of the attendees cannot eat gluten, and not having a dessert that was safe for them seemed cruel), lots of good beer, and oh, yes... Flank steak tacos.
These tacos are made with a recipe based off Cooks Illustrated, which I have since tweaked significantly. The method is the same, and it is a good one. Flank steak is a tough, cheap cut of beef, but it has a lot of flavor and most of the stringiness can be mitigated simply by cutting across the grain. This particular cut of meat makes figuring out where the "grain" is supremely easy: simply look at your steak, and take note of the muscle striations (they are really obvious--it's the long lines running across the cut of meat in the same direction on both sides). When you cut it, cut perpendicular to those lines, and make the slices as thin as your knife sharpness will allow. Because the muscle fibers are cut short, the pieces become tender and delightful. Stabbing it with a fork makes sure that the marinade gets into the piece of meat, helps cut some of those long muscle fibers, and is also oddly satisfying.
This is a paste-style marinade that comes together in a few minutes, and as little as half an hour lends a lot of flavor, making it ideal for a quick weeknight supper.
Cram everything but the steak into a food processor and pulverize it until you have a reddish-brown paste full of pretty little green flecks. Take your flank steak out and put it in a large baking pan or sheet. Pretend it is someone you hate, and stab repeatedly with a fork. Turn the steak over, repeat stabbings. Spread enough of the paste on each side to make a thin coating, and allow it to sit for at least 30 minutes. I let it sit on the counter (provided I can watch it--we have two labrador retrievers who think that things like steak and butter and apples left at counter-level are just dog treats we forgot to give them) so it can come to room temperature. You will likely have some marinade left over; save it and you can use it as a sauce, or freeze it for later use.
Once the 30 minutes are up, place a large skillet on medium-high heat, or pull out your handy electric skillet (I have this one and I love it) and crank that sucker up. Add a little vegetable, corn, or other oil with a high smoke point to said skillet.
Scrape most of the marinade paste off the meat. Burnt garlic is no one's friend. Sear the steak until browned and a little crusty, probably about 8 minutes or so per side. Cooking time will vary if you have an unusually thin or fat flank steak, or if you prefer yours more well-done (or still mooing). Once it is cooked, remove it from the heat and let it rest for a few minutes, then slice as thinly as possible.
While the meat tends to retain a lot of flavor, if you want a sauce, add a little more olive oil and some lime juice to the reserved marinade and drizzle over your steaky goodness.
This is a recipe that is easily doubled or tripled, and you can tweak it to your liking. My spicy-intolerant family had no problem with the chipotles, and if you like more heat, you can always toss some jalepeno or other peppers into the marinade.
This can be served with the usual taco toppings, or you can go a little more unusual (but no less tasty) with blue cheese, carmelized onions, and sauteed garlicky spinach on corn tortillas. Which is what we did. It was delicious.