Brioche dough happens to be a great alternative to the traditional puff pastry. The reason behind is that puff pastry is likely to end up undercooked and unfortunately many chefs fall short. Pretty much any item can be wrapped in pastry and be sold as 'Wellington'. Yeasty dough offers better outcome because the way it behaves. If using puff pastry, I would definitely recommend the use of the inverted puff pastry, rolled out into a 3mm thick sheet. For the brioche recipe and how to trim beef tenderloin watch the videos.
Soak mushrooms in cold water for a min. Drain and pat dry. Trim off foot quarter. Process mushrooms into duxelles (coarse) in a food processor. Sauté the mushrooms in a skillet without any seasoning until the moisture evaporates. Let cool completely.
Season filet generously with salt. Heat up a frying pan, drizzle oil and sear filet for about 3 min in each side. Remove from the pan, brush meat with mustard and season with pepper; set aside.
Arrange sliced prosciutto on plastic wrap and spread mushroom duxelles. Place the beef filet in the center and wrap up into a tight cylinder and chill 20 minutes. Lightly flour work surface and roll out dough into a 1/8''/4mm thick rectangle. Brush the edges with egg wash. Remove the plastic wrap from the beef and place in the center of the dough. Fold the ends over and wrap the pastry around the tenderloin, seal and trim off excess dough. Chill for 10 min to rest. Place the Wellington on baking tray and egg wash the whole log twice. Using the tip of a pairing knife, score the Wellington into desired patterns.
The use of a pizza stone is recommended. To find pizza stone click here
Set oven temperature to 375ºF/190ºC. Bake Wellington for 40 minutes, or until the center of the meat reaches 125ºF/52ºC. Do not overcook, beef filet should be served medium-rare. The crust holds in steam and heat, thus enhancing the effects of carryover cooking. Let rest 20 minutes before carving. Slice and season with fleur de sel and ground black pepper. Enjoy!