Last Updated on April 25, 2015 by SteakEat

Let’s find out how to sous vide flat iron steak using a simple Dutch oven.

Here I will explain the actual method and you will understand things like steak thickness, required cooking time and so on.

I broke down this guide into three parts to make navigation easier for you.

Part 1: Sous Vide Round Steak – The Method. What exactly is sous vide and how we use it to cook the most succulent flat iron steak.

Part: 2: Buying Guide & Utensils. How to buy a perfect steak and which cooking tools to use in more detail.

Part 3: Pro Tips on Sous Vide. Make your cooking even easier and try some recipes.

Part 1: Sous Vide Round Steak – The Method

What Is Sous Vide?

Sous vide is French and literally translated means “under vacuum”.

Meats, fish, poultry, or vegetables are sealed in an airtight bag and cooked very slowly for a long time, in some cases as much as 72 hours in warm water.

What You Need

Even though there are numerous options for buying sous vide circulators and water ovens, it doesn’t mean you can’t sous vide without them.

Here is what you need for a no-frills method:

• Flat iron steak
• Salt (ideally kosher)
• Freshly ground black pepper
• Dutch oven
• Food-safe plastic bag*
• Paper towels
• For searing steak: Blowtorch or Skillet with 1 tbsp of coconut oil / ghee

How Does It Work

The long slow cooking tenderizes the food and ensures that it is cooked throughout, without overcooking the outside.

Cooking a flat iron steak in this way ensures that it is cooked to the same level throughout the meat, something that is particularly difficult to do with conventional cooking techniques.

This way meat requires two stages of cooking.

First, we use a Dutch oven to cook the meat throughout.

Second, we sear the outside of the steak to create the attractive browned look normally associated with the best steaks.

It is a technique that is particularly useful for cooking large, oversized steaks that overcook on the outside before the middle is cooked to the right amount.

You can make flat iron steak very tender with sous vide cooking.

Steak Cooking Times for Sous Vide Method

Core temperature is the best way of determining how well cooked your flat iron steak is. A rare steak needs to reach a temperature in the middle, known as core temperature, of 50C / 122F.

Medium rare is at 55C / 130F and medium at 60C / 140F.

The time to reach the required core temperature will be determined by the thickness of your flat iron steak.

The thicker the steak, the longer time it will take to come to temperature.

The core temperature is reached by immersing the steak into a bath of water with the required temperature.

Work out your flat iron steak sous vide time here:

Thickness                           Required cooking time

0.25 inches                        23 minutes
0.5 inches                           31 minutes
1 inch                                   60 minutes
1.5 inches                           1 hour 45 minutes
2 inches                               2 hours 50 minutes
2.5 inches                           4 hours 15 minutes
3 inches                               6 hours

Even though the times for thicker steaks look very long, remember that you do not need to be babysitting your steaks while they are cooking.

Remember – you cannot overcook a steak when you use the sous vide technique as the core temperature will never go above the temperature of the water in the water bath.

And now – let’s cook.

Stage One – The Gentle Cook

Cooking your flat iron steak sous vide requires careful planning but is very easy.

Once again, here is all you need for this simple guide:

• Flat iron steak
• Salt (ideally kosher)
• Freshly ground black pepper
• Dutch oven
• Candy/oil thermometer
• Food-safe plastic bag*
• Paper towels
• For searing steak: Blowtorch or Skillet with 1 tbsp of coconut oil / ghee

Fill up Dutch Oven

Start with a Dutch oven and fill it about 2/3 full of warm water. Ideally fix a candy or oil thermometer so that it measures the temperature of the water.

Bring it to the desired temperature on the stove or inside the oven (I recommend oven, since it gives a more even heat).

Adjust the Temperature

Increase the temperature of the water to the correct temperature over a medium heat. So if you’d like a medium-rare flat iron steak, go for 55C / 130F.

Zip the Steak

Place the steaks into a zip lock plastic food-safe bag and squeeze out all of the air before sealing the zip lock*.

Note that we don’t add any salt or pepper. We will do it in stage two, so that we don’t destroy our steak when cooking it with salt for too long.

You can however add dry rubs at this stage – more on that in Part 3.

Sous Vide

Immerse the steak bag in the Dutch oven with the temperature set according to the level of doneness you want to achieve (55C / 130F for medium-rare) and cook it for the time required depending on thickness:

Thickness                           Required cooking time

0.25 inches                        23 minutes
0.5 inches                           31 minutes
1 inch                                   60 minutes
1.5 inches                           1 hour 45 minutes
2 inches                               2 hours 50 minutes
2.5 inches                           4 hours 15 minutes
3 inches                               6 hours

Remember – you can’t overcook the steak, if the temperature is fixed, but…

This can be hard to achieve with a conventional stove top and oven – temperature control is a tricky thing to adjust, especially if you are dealing with gas cookers and older electric cookers which may be quite inaccurate.

If you find yourself falling in love with sous vide, I recommend you either get a sous vide minioven or an immersion calculator like this.

* There were some health concerns, regarding plastic leaching endocrine disrupting chemicals into food (not just during cooking). As for now sous vide community found the least harmful alternative to “food-safe” plastic zip lock bags – silicone bags, which can be used more than once. 

Stage Two – The Sear

A chef’s blow torch is the perfect way of searing a steak that has been cooked sous vide, but it’s not a must-have. Regular stove top skillet will do just as well – all you need is to really heat it up well.

Let’s start with the blow torch instructions and then look at how we can use skillet instead.

Searing Flat Iron Steak with Blow Torch

The aim is to sear the outside without affecting the meat immediately inside.

Remember, the whole point of sous vide is to have a consistently cooked piece of steak so the thin crust that a flat iron steak will take on after searing with a blow torch is perfect.

To sear your flat iron steak after sous vide:

• Remove it from the zip lock bag after the required amount of time has passed.
• Pat it completely dry with paper towels.
• Season with coarse kosher salt.
• Light your blow torch and turn it to the highest heat.
• Apply the flame evenly to the surface and edges of the flat iron steaks until a golden browned crust develops.
• Season your steak with freshly ground pepper.
• Then cut and serve.

HINT: Make sure it’s a professional blow torch, which can generate enough heat to sear the steak immediately. Less powerful torches, often used for creme brulees, will not have the same effect.

Searing Flat Iron Steak in Skillet After Sous Vide

The goal is to sear the steak surface as quickly as possible. It means you should heat up the skillet really well.

• Remove the steak from the bag, pat it dry with paper towels and season with kosher salt.
• Add a tablespoon of ghee or coconut oil to the skillet and heat it up. You will know it’s ready, when you see gentle smoke coming off it; then wait for another 10 seconds to make sure the pan is hot enough.
• Put the steak inside the skillet and sear it for 1 minute per side so it develops the surface browning.
• Once ready, rest the steak for two minutes on a plate, season with freshly ground black pepper, cut and serve.

This is all you need to know to cook a flat iron steak using sous vide technique.

And now I invite you to Part 2 where I will better explain how to buy a perfect flat iron steak and show you which cooking utensils you can use in more detail. You can also check out sous vide tips and recipes in Part 3.
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