Flank Steak: To Cast Iron or To Sous Vide?

We bought a giant pack of flank steak from Costco, so we decided to try two different methods of cooking for dinner! The first is a salt & pepper flank steak recipe cooked on a cast iron pan (see below), and the second is our favorite fajita-style flank steak recipe cooked sous vide (posted previously here).

At the end of the post, we’ll share our thoughts on which method we thought was better.

Salt & Pepper Flank Steak

We’re not joking when we say this is salt and pepper flank steak. That’s pretty much all there is to it. And a cast iron pan with oil, of course.


  • Flank steak
  • Salt to taste
  • Pepper to taste
  • 3 tbsp olive oil


Step 1. Chop the flank steak into steak-sized chunks, add 2 tbsp olive oil, and season with an abundance of salt and pepper to taste. (Remember this is only coating the outer surface of the steak, so you may need to add more than usual.)

Step 2. Heat the cast iron pan on high and add 1 tbsp oil. Add flank steaks and cook for 2 minutes per side for medium rare. (This particular steak was pretty thin, so it almost cooked completely through.)

Step 3. Remove steaks from heat and let cool before slicing into strips and serving.

To cast iron or to sous vide

We served the salt and pepper cast iron steak next to our sous vide steak, and quite honestly, both of them were delicious! However, you can definitely tell a difference between the two cooking methods, both in texture and in appearance. To be fair, the two pieces of steak were not the same thickness, and the marinade was different, so sadly this is not a scientifically sound comparison.

In the pictures below, the 4 pieces on the left were cooked in the cast iron pan, and the 3 larger pieces on the right were sous vide’d and then seared in the cast iron for 1 minute on each side.

Our impressions:

Disregarding the fact that these were two completely different marinades and the steaks weren’t quite the same thickness, here are our impressions about the two different cooking methods!

Category Cast Iron Sous Vide
Time to Cook Extremely quick (~5 minutes)  A long time! ~2 hours, depending on the thickness of the steak, although you don’t have to “actively” cook until you sear
Texture of the Steak A little chewy (possibly due to the thin steak we had) Soft and moist! almost like eating wagyu beef, except much cheaper
Meat Flavor Flavor is all in the outer coating, while the inside tastes beefy (of course, this also depends on how long you marinate for) The marinade can sometimes overpower the meat flavor because the meat soaks for so long
 Appearance Unevenly cooked. There is a gradient from well done at the edges to possibly raw in the center. Homogenously cooked. Can appear very red even though the steak is cooked medium or medium well. Searing after sous vide is needed to prevent the steak from looking “pasty”, which adds a small layer of well-done meat on the surface.
 Final Thoughts Good for quick dinners, short marinade recipes, crispier steaks Good for flavor infusion with complicated marinade recipes, creates juicy and tender steaks

In conclusion, we love both methods of cooking, and choosing between the two usually boils down to how we feel that day!


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