Directions

1. Add mushrooms, 2 shallots, garlic, and 2 sprigs of thyme leaves to a food processor and pulse until finely chopped. Add 2 tablespoons butter and 2 tablespoons olive oil to a large saute pan and set over medium heat. Add the shallot and mushroom mixture and saute for 8 to 10 minutes until most of the liquid has evaporated. Season with salt and pepper and set aside to cool.
   
2. Tie the tenderloin in 4 places with kitchen twine. Drizzle with 1 tablespoon olive oil, then season with salt and pepper. Sear all over, including the ends, in a hot, cast iron skillet lightly coated with 1 tablespoon olive oil, about 2-3 minutes. Take out and let cool on a plate.
   
3. Meanwhile, set out your prosciutto on a sheet of plastic wrap 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 spatula cover evenly with a thin layer of mushrooms. Season the surface of the mushroom with salt and pepper and sprinkle with thyme leaves from 6 sprigs.
   
4. Cut off twine from beef and smear lightly all over with Dijon mustard. Allow to cool for 10 minutes, then roll up in the mushrooms 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. Set in the refrigerator for 30 minutes to overnight ensure it maintains its shape.
   
5. Preheat oven to 425 degrees F. In a small bowl crack egg and lightly beaten. On a lightly floured surface, roll the puff pastry out to about a 1/4-inch thickness. You may have to overlap 2 sheets and press them together.
   
6. Remove beef from refrigerator and cut off plastic. Set the beef in the center of the pastry, then trim ends if necessary. Roll the beef with the pastry. Close the ends and tuck the pastry underneath. Place beef seam side down on baking sheet with parchment. Add trimmings as decoration then brush the entire pastry with egg wash. Top with coarse sea salt.
   
7. Make a couple of slits in the top of the pastry using the tip of a paring knife. Bake for 40 to 45 minutes until pastry is golden brown and beef registers 125 degrees F on an instant-read thermometer. Remove from oven and rest before cutting into thick slices.
   
8. Meanwhile, in cast iron skillet used to sear the beef add 1 tablespoon butter and 1 tablespoon olive oil. When the butter has melted, add 1 shallot. Cook for 2-3 minutes until the shallots are just starting to soften. Add 4 cloves garlic and cook, stirring often for another 30 seconds. Stir in the flour and cook for a further 30 seconds.
   
9. Add in the red wine while stirring, then add in the beef broth. Stir again and bring to the boil. Simmer for 10-15 minutes, stirring occasionally until thickened and reduced by one third. Season to taste then stir in the parsley. Serve with wellington.