Prepare the necessary ingredients.
Wash the individual pieces of beef tenderloin, dry them with a towel, season with salt and pepper, and then quickly sear in a hot pan for 2 minutes on each side.
450 g beef, ½ tsp salt, ½ tsp pepper
Lay the seared pieces of meat on a board, let them cool a bit, coat with mustard, and leave for 15 minutes to cool completely.
2 tsp mustard
While the beef is cooling, prepare the mushroom duxelles. First, finely chop the onion.
1 pc onion
Then finely chop the mushrooms. This can be done with a knife or a blender.
400 g mushroom
Season the onions and mushrooms with a little salt and pepper, add thyme sprigs, and sauté in butter for 10-12 minutes or until all the liquid has evaporated.
1 pc onion, ½ tsp salt, ½ tsp pepper, 2-3 sprig thyme, 50 g butter
At the end of cooking the mushrooms and onions, add vermouth. Bring the duxelles to a boil and again evaporate all the liquid.
⅓ cup vermouth
Assemble the filling for the pastry. To do this, lay a couple of slices of prosciutto on a double layer of plastic wrap, on top of which place a tablespoon of mushroom duxelles and a piece of beef fillet.
55 g hamon, 450 g beef
Tightly wrap each portion of meat in prosciutto and pack in food wrap, then refrigerate for at least 1 hour, or better overnight.
After the meat has cooled well, wrap each piece in a sheet of thinly rolled puff pastry and tightly pinch the edges.
250 g puff pastry
Lay the fillet wrapped in pastry seam down on a baking sheet lined with parchment. Make a small incision on top of each piece and brush with liaison (a mixture of raw egg yolk and a tablespoon of water).
Bake the beef in an oven preheated to 220˚C. For a medium doneness, the meat should stay in the oven for 25-30 minutes.
Let the dish rest for 10-15 minutes, then cut each portion in half and serve. Bon appétit!