Encrusted with earthy cumin and bright coriander, this sous vide flank steak is impossibly tender, deeply flavorful and marvelously easy to make. Serve it with a vibrant fresh herb sauce that's spiked with parsley, cilantro and just the right touch of jalapeño pepper. Or skip the herb sauce, and make fermented salsa verde instead - and then slice and serve the flank steak for fajitas.
Why sous vide works so well for flank steak.
Sous vide is a culinary technique that's commonly used in upscale eateries, but has recently become popular among home cooks, too. The technique, which means "under vacuum," involves cooking vacuum-sealed foods in a water bath that is held at a constant temperature.
That results in meat that is very tender and consistently cooked. Accordingly, cooking meat with sous vide gives even the toughest cuts of meat tenderness. So grass-fed meats, which tends toward toughness, and flank steak do particularly well with this technique.
The constant temperature and prolonged cook time allow enough time to let the steak's collagen and fat liquefy without overcooking the meat. So meat is consistently tender, and deeply flavorful every time you cook.
Making Sous Vide Flank Steak
Cooking steak with sous vide involves a few simple steps. You'll start by seasoning your steak. Next, you'll vacuum seal it to remove all the air before plunging it in a water bath heated by an immersion circulator. After cooking, sear it in a very hot cast iron skillet so that it develops a nice crust and then serve it warm.
But, there's three basic steps you need to pay particular attention to: Vacuum sealing, temperature and timing. Here's why.
In order for your steak to cook through evenly and safely, you need to remove all air from the bag that will hold it. The best way to do this is to vacuum seal it.
I use the FoodSaver FM2000 which is affordably priced, and it tucks neatly away in the cabinet when I don't need it. It's the best-selling brand, and it comes with a 5-year limited warranty. It's also ETL safety certified.
Pro-Tip: You can also use the FoodSaver to preserve your garden harvest, or to vacuum seal leftovers before you freeze them - keeping them fresher.
When cooking with sous vide, your temperature should be constant - so that the steak cooks evenly and consistently all the way through. For sous vide flank steak, recipe temperatures vary from 129 F to 134 F. With 129 F produce rare steak and 134 F producing medium-well steak.
This recipe calls for setting your immersion circulators temperature to 131.5 F, which produces a nice medium-rare steak - even after searing it at the very end.
Since you cook your steak at the optimal temperature, it's hard to overcook. So cook it long enough for the connective tissue and fat to liquefy and melt (at least 2 hours) and up to 12 hours. You can even toss the steak into the water bath in the morning, and it'll be ready and warm for dinner.
Tips for Sous Vide Flank Steak
- Use a vacuum sealer to seal your bags. In order for the steaks to cook properly, you must remove all the air from their packaging. And that's why a vacuum sealer is integral to sous vide cooking.
- Use food-grade plastic bags designed for sous vide cooking. Because the plastic is heated, you'll want to be careful with which bags you select. So, use food-safe plastic made without BPA or pthalates. I use FoodSaver bags because they work well for sous vide, are free from BPA and pthalates and made from food-safe polyethylene and nylon.
- Temperature is important. Your immersion circulator keeps temperature constant, even and without cold or hot spots - and that means your food cooks safely and evenly.
- Sear the steak to finish it. While sous vide flank steak is safe to eat as soon as it comes out of the water bath, searing it gives a nice caramelization - developing that delicious, rich crust.
- Vacuum seal your leftovers. You can tuck your leftovers into a FoodSaver bag, vacuum seal it and toss it into the freezer for an easy meal later.