Flank steak has become our go-to choice when indulging in steak. When it’s on sale at our local grocery, I always snap one up. Because it’s so lean, it definitely benefits from some extra care. I’ve cooked flank steak many ways, but by far the best is sous vide.

The beauty of sous vide is its flexibility. If we’re not in the mood for steak the day we buy it, I season it, vacuum seal it and freeze it. When we’re ready, I drop it in the sous vide straight from frozen and simply add an extra 45–60 minutes to the cooking time.

Why Steak Frites?
If I had to pick my last meal, it would be either steak frites or pizza. I’ve tried this dish at restaurants all over the world. Some come with au poivre, a bearnaise, straight up butter, others with blue cheese but my favorite is always chimichurri. I love the simple, garlicky, herbaceous sauce. It pairs perfectly with the steak and if you get some on your frites, even better.

Steak frites is a meal on its own, but we like to add a side of vegetables. My choice? Asparagus, roasted under the broiler with a little olive oil, salt and pepper.

I’ve also posted my Air-Fried Duck Fat Skinny Fries with Truffle Sea Salt before; for this version, I simply used the thicker fry setting on the mandoline slicer for a more traditional French fry.

My chimichurri is the same as usual fresh, garlicky, herbaceous, and bright.

At the bottom there is a bonus recipe for Cowboy Butter which also goes very well with steak frites.

Special Equipment: Vacuum sealer, sous vide, mandoline slicer, air fryer.

Ingredients

Ingredients for Sous Vide Flank Steak

1 large flank steak
2 tbsp Montreal Seasoning (or salt and pepper)
3-4 sprigs of thyme (or other herb like rosemary)

Ingredients for Air Fried, Duck Fat and Truffled Frites

4-5 medium potatoes (russet or yukon gold)
Duck fat spray or olive oil
Truffle sea salt to taste

Ingredients for a Chimichurri Sauce

1/2 cup cilantro, minced
1/2 cup parsley, minced
2-4 cloves garlic, minced
1-2 tbsp red wine vinegar
1 tsp + crushed red pepper flake
1-2 tbsp olive oil
Salt and pepper to taste

Instructions

How to make Sous Vide Flank Steak

Season the flank steak generously with Montreal seasoning and place it in a vacuum-sealable bag with thyme. Vacuum seal.
Preheat the sous vide to 120°F for medium-rare. (Increase to 125–130°F if you prefer more doneness.)
Place the sealed steak in the sous vide and cook for 2–4 hours.
Remove the steak, discard the thyme and pat dry thoroughly.
Heat a large stainless steel or cast iron skillet over high heat and add a tablespoon of neutral oil.
Sear the steak on both sides until browned.
Remove from the pan and allow to rest 5–10 minutes before slicing against the grain.

How to make Air Fried, Duck Fat and Truffled Frites

Slice the potatoes with a mandoline using the standard French fry setting.
Place the fries in a large bowl and rinse under cold water. Soak for at least 10 minutes to remove excess starch.
Drain and dry thoroughly with a towel.
Preheat the air fryer to 400°F and spray with duck fat.
Toss the fries with duck fat and cook in batches if needed. Cook for approximately 25 minutes, tossing every 5 minutes.
Season with truffle sea salt to taste.
Keep cooked fries warm in a preheated 200°F oven while finishing the rest.

How to make a chimichurri Sauce

In a medium bowl, combine cilantro, parsley, garlic, crushed red pepper flakes and red wine vinegar.
Stir to combine and season with salt and pepper to taste.
Refrigerate until ready to serve.