Preheat your sous vide machine to your desired doneness (for example, 130°F for medium-rare).

Season the filet mignon steaks with salt and pepper on all sides.

Submerge the sealed steaks in the sous vide water bath, ensuring they are fully underwater. Cook for 1 hour.

Once cooked, remove the steaks from the bags and pat them dry with paper towels to remove excess moisture.

Heat a skillet over high heat and add the cooking oil and butter.

Once the butter is melted and the skillet is hot, sear the steaks for 1 minute on each side, spooning the butter over the steaks as they sear.

Serve the steaks immediately after searing.