Season the chateaubriand with salt and pepper and tie the chateaubriand with twine

Heat an empty skillet on medium heat and brown the outside of the chateaubriand for 30 seconds on each side.

Let it rest for 30 minutes in the fridge, then add to a plastic sous vide bag with 2 tabs of butter and 3 sprigs fresh thyme.

Sous vide the chateaubriand for 2 ½ hours at 120-125 degrees fahrenheit.

While the chateaubriand is in the sous vide, mince the mushroom, shallot and 3 springs thyme in a food processor or by hand.

Cook the mushroom mixture at a low to medium heat for 30 minutes to reduce it and have the liquid from the mushrooms evaporate.

Rest the chateaubriand and the mushrooms (uncovered) overnight in the fridge.

The following day, defrost your puff pastry per the directions on the box.

Lay plastic wrap out, and put 3-4 oz of prosciutto overlapping on the plastic wrap

Add a layer of the mushroom mixture on top of the prosciutto.

On a cutting board, coat the chateaubriand with the dijon mustard.

Place the coated chateaubriand on top of the mushroom layer on one side and roll the mushroom and prosciutto layers over the meat.

When the chateaubriand is fully wrapped in the prosciutto and mushrooms, wrap the plastic wrap tightly around it all to hold the form and place it in the fridge for an hour.

Preheat your oven to 400 degrees fahrenheit.

After an hour, roll the defrosted puff pastry out, using a sprinkle of flour to prevent sticking.

Place the chateaubriand on one side of the puff pastry and roll it over to full inclose the meat.

Coat the puff pastry in an egg wash and salt over the top

Bake the beef wellington at 400 degrees F until your puff pastry is gold brown, ours took about 30 minutes.

Let it rest for 5+ minutes, slice the roast, and enjoy.