Beef Wellington with Roasted Potatoes and Wilted Greens

Ingredients:
1 1/2 pounds white button mushrooms
2 shallots, roughly chopped
4 garlic cloves, roughly chopped
2 thyme sprigs, leaves only
2 tablespoons unsalted butter
2 tablespoons extra-virgin olive oil
Kosher salt
freshly ground black pepper
1 (3-pound) center-cut beef tenderloin (filet mignon), trimmed
Extra-virgin olive oil
Kosher salt
freshly ground black pepper
12 thin slices prosciutto
6 fresh thyme sprigs, leaves only
2 tablespoons Dijon mustard
Flour, for rolling out puff pastry
1 pound puff pastry, thawed if frozen
2 large eggs, lightly beaten
1/2 teaspoon coarse sea salt
Thinly sliced chives, for garnish
2 tablespoons extra-virgin olive oil
2 shallots, sliced
2 garlic cloves, smashed and peeled
3 thyme sprigs, leaves only
1 cup brandy
4 cups low-sodium beef stock
2 cups heavy cream
2 tablespoons grainy mustard
1/2 cup green peppercorns in brine, drained, brine reserved
1 1/2 pounds fingerling potatoes, scrubbed
2 fresh rosemary sprigs
2 to 3 sage sprigs
3 thyme sprigs
6 garlic cloves, left unpeeled
3 tablespoons extra-virgin olive oil, plus more for sheet pan
Kosher salt
freshly ground black pepper
1/4 cup honey
1/2 cup balsamic vinegar
1 cup walnuts, for garnish
3 bunches assorted winter greens (such as Swiss chard, radicchio, or escarole), washed, stemmed, and torn into pieces
1 tablespoon grainy mustard
Extra-virgin olive oil
1/2 cup pomegranate seeds, for garnish
Parmesan shavings, for garnish
1 shallot
chopped
for garnish

Instructions:
Add mushrooms, shallots, garlic, and thyme to a food processor and pulse until finely chopped. Add butter and olive oil to a large sauté pan and set over medium heat. Add the shallot and mushroom mixture and sauté until most of the liquid has evaporated, 8 to 10 minutes. Season with salt and pepper and set aside to cool.
Tie the tenderloin in four places so it holds its cylindrical shape while cooking. Drizzle with oil, then season with salt and pepper. Heat a large, heavy-based skillet over medium-high heat and lightly coat with oil. Sear the beef all over, including the ends, until dark brown, about 2 to 3 minutes.
Meanwhile, set out your prosciutto on a sheet of plastic wrap (plastic needs to be about a foot and a half in length so you can wrap and tie the roast up in it) on top of your cutting board. Shingle the prosciutto so it forms a rectangle that is big enough to encompass the entire filet of beef. Using a rubber spatula, evenly cover the prosciutto with a thin layer of duxelles. Season the surface of the duxelles with salt and pepper and sprinkle with thyme leaves.
When the beef is seared, remove from heat, cut off twine and smear lightly all over with Dijon mustard. Allow to cool slightly, then roll up in the duxelles covered prosciutto using the plastic wrap to tie it up nice and tight. Tuck in the ends of the prosciutto as you roll to completely encompass the beef. Roll it up tightly in plastic wrap and twist the ends to seal it completely and hold it in a nice log shape. Chill in the refrigerator for 30 minutes to ensure it maintains its shape.
Preheat oven to 425°F.
On a lightly floured surface, roll the puff pastry out to about a 1/4-inch thickness. Depending on the size of your sheets, you may have to overlap two sheets and press them together. Remove beef from refrigerator and cut off plastic. Set the beef in the center of the pastry and fold over the longer sides, brushing with egg wash to seal. Trim ends if necessary then brush with egg wash and fold over to completely seal the beef, saving ends to use as a decoration on top if desired. Top with coarse sea salt. Place the beef seam side down on a baking sheet.
Brush the top of the pastry with egg wash, then make a couple of slits in the top of the pastry using the tip of a paring knife. Doing this creates vents that will allow the steam to escape when cooking. Bake until pastry is golden brown and beef registers 125°F on an instant-read thermometer, 40 to 45 minutes. Remove from oven and let rest for 15 minutes before cutting into thick slices. Garnish with minced chives, and serve with Green Peppercorn Sauce, Roasted Fingerling Potatoes, and Warm Wilted Winter Greens.
Add olive oil to pan after removing beef. Add shallots, garlic, and thyme; sauté for 1 to 2 minutes, then, off heat, add brandy and flambé using a long kitchen match. After flame dies down, return to the heat, add stock and reduce by about half. Strain out solids, then add 2 cups cream and mustard. Reduce by half again, then shut off heat and add green peppercorns.
Preheat oven to 500°F and place a baking sheet inside.
Add potatoes, rosemary, sage, thyme, and garlic to a medium bowl. Drizzle with olive oil, and season with salt and pepper. Remove baking sheet from oven, lightly coat with olive oil, and pour potatoes onto pan. Place potatoes in oven and reduce heat to 425°F. Roast until crispy on outside and tender on inside, about 20 minutes.
In a large sauté pan, cook honey and balsamic together over medium-high heat for 5 minutes. Toast walnuts in a small skillet; set aside to cool.
Pile greens on a platter. Stir mustard into balsamic-honey mixture, then whisk in about 1 cup extra-virgin olive oil; pour over greens. Season greens with salt and pepper and garnish with walnuts, pomegranate seeds, shavings of Parmesan, and shallot.