First, prepare sous vide water bath by filling a large pot with water. The pot needs to be large enough to hold your steak and the water needs to be deep enough to hit the water line on your sous vide. Next, place your sous vide into the water bath. For a medium-rare steak, set the water bath to 130ºF. See the recipe notes for other temperature recommendations.
Next, generously salt and pepper both sides of the steak and place steak into a medium-sized Stasher bag or Food Saver bag. Each steak should be placed in its own bag, so if you're cooking 4 steaks, use 4 bags.
Next, place 1 tablespoon of butter on top of each steak and a sprig of herb.
Remove the air from all of the bags and tightly seal them. If you're using a Stasher bag, try your best to remove as much air as you can.
Place steaks into the preheated water bath and cook at 130ºF for 2-4 hours. 2 hours is enough time to get the entire steak to the proper temperature, but you can cook for up to 4 hours before the tendons start to break down.
After 2 hours, remove the steak from the water bath and transfer it onto a plate.
Now it's time to sear the steak for that amazing texture. Heat a cast iron skillet over medium-high heat. When pan is hot, add the olive oil.*
When olive oil is fragrant, place the steak in the pan and sear for 1 minute per side. Then, immediately remove them from the heat.
Serve with chimichurri or a delicious vegetable side.