Beef: 

1. Season the tenderloin generously on all sides with kosher salt and freshly cracked black pepper. Optionally, let the meat temper for about 20 minutes at room temperature to get a better sear.
2. Heat a large skillet over medium-high, and once hot, add enough neutral oil to coat the bottom of the pan in a thin, even layer. Pat the tenderloin dry with paper towels on all sides. Gently press the steak into the pan and sear for about 1 minute per side, including the ends. Transfer to a baking sheet and immediately brush all over with Dijon mustard. Place the meat in the fridge while you prepare the duxelles. Optionally, reserve the pan to make the sauce later.

Duxelles:

1. To the bowl of a food processor, add the mushrooms, shallots, and garlic. Pulse, scraping down the sides as necessary, until the mixture is finely chopped.
2. In a large skillet over medium heat, add the olive oil and, once hot, add the processed vegetables. Season to taste with salt and pepper. Cook, stirring occasionally, until most of the moisture has evaporated and the duxelles resembles a thick, paste-like consistency. Optionally, add in the thyme and toss to combine.
3. Transfer to a sheet tray and spread into a thin, even layer. Place uncovered in the fridge to cool until ready to use.

Wellington:

1. On your work surface, press down a large sheet of plastic wrap as flat as possible. You may need to layer 2 smaller sheets of plastic wrap adjacent to each other to create the surface area needed for rolling.
2. In the center of the plastic wrap, shingle 3 slices of prosciutto next to each other, then overlap another 3 slices on top of the first row to create a tall rectangle. Leaving a ½” border of prosciutto, spread your cooled duxelles evenly across the lower ⅔ of the rectangle. Place the cooled beef in the center of the lower ⅓ of the duxelles.
3. Grab the bottom edge of the plastic wrap and carefully roll over the tenderloin until it is enclosed. Crimp the edges shut, then lightly twist the sides of the plastic wrap to tighten the Wellington into a more compact log. Place in the fridge while you make the egg wash and roll out the puff pastry.
4. In a small mixing bowl, whisk together the egg yolks and water. Lightly dust your work surface and puff pastry with flour to prevent sticking. Using a rolling pin, roll the pastry out until it is slightly less than ¼” thick and is a rough 16x16” square. Cut the pastry so its width extends about 2-2.5” beyond the sides of the rolled Wellington. Optionally, reserve the excess pastry to make a lattice pattern.
5. Carefully remove your chilled Wellington from the plastic wrap, then place in the center of the lower ⅓ of the pastry. Brush a 1” perimeter of egg wash along the bottom edge and sides of the pastry. Grab the bottom edge of the pastry and pull up until it meets the Wellington. Roll forward like a burrito until just before the puff pastry meets itself. Leaving about 1” of pastry on the Wellington side, cut off the excess dough. Brush the final edge with egg wash, then finish rolling to enclose the Wellington. Press the edges of the dough down onto itself to close the edges of the Wellington, then cut off any excess pastry along the sides.
6. Place your Wellington onto a sheet of plastic wrap, roll like a burrito, then gently twist the sides to close and make its shape more uniform. Place in the fridge then preheat your oven to 400°F (204°C) convection, or 425°F (218°C) regular.
7. Once the oven is hot, remove the Wellington from the plastic wrap and place on a parchment-lined, lightly greased baking sheet. Brush the entire surface with an even layer of egg wash. Optionally, lay on your lattice pattern pastry, trimming any excess overhang, and brushing with additional egg wash. Top with a generous amount of flaky salt and bake for about 20-30 minutes, or until it reaches your desired internal temperature and the exterior is golden brown. *see Notes*
8. Transfer the cooked Wellington to a wire rack set over a baking sheet and let rest for a minimum of 5 minutes.

Au Poivre:

1. In your reserved steak pan, add the butter and set over medium heat. Once the butter is melted and bubbling, add the shallot, garlic, and peppercorns, and saute, stirring often, until softened, about 2-3 minutes.
2. Pour in the beef stock, increase the heat to high, and reduce for about 2 minutes, or until slightly thickened. Add the heavy cream, and reduce again until slightly thickened, another 2-3 minutes. Stir in the Worcestershire sauce and lemon zest. Turn off the heat and swirl in the cold butter until melted and emulsified. Season to taste with salt.

Broccolini:

1. In a large saute pan heated over medium high, add enough oil to coat the bottom. Once hot, add your broccolini, tossing to coat with the oil. Allow to sear undisturbed for 1-2 minutes, then toss. Repeat this 1-2 more times, adjusting the heat as necessary, until there is some light char and caramelization on all sides, about 5 minutes. The vegetables should be cooked through but still have some crunch. Season to taste with salt, finish with lemon juice, toss, and reserve until serving.

Serving:

1. Slice your Wellington in half and serve however you like! I plated mine with my Robuchon mashed potato recipe, broccolini, and au poivre. Serve and enjoy!

*Notes*

• Any mustard you have on hand will do!
• Make sure the prosciutto is sliced in a way that it stays 100% intact. Pre-sliced is usually the best move here.
• The meat will carry over cooking after it has been removed from the oven, so I recommend pulling it about 10-15 degrees under where you want it to end up.