Season beef with olive oil, salt and pepper then roast beef for 12-15 min in a preheated 210 degree oven
Meanwhile pulse mushrooms, garlic, shallots and thyme in food processor until they have the texture of coarse breadcrumbs, stopping before they become a slurry
Melt butter in pan with olive oil over medium heat. Add mushroom mix and cook for 8-10 min until softened.
Add white wine and cook until mixture holds its shape when stirred. Season with salt and pepper.
Lay two overlapping rows of prosciutto on glad wrap and spread half of the mushroom mix (duxelles) over the middle, overlapping section of the prosciutto
Cut twine from beef and paint a thin layer of dijon over roast
Place beef in the middle of the prosciutto (on the area covered with duxelles) and cover the top of the beef roast with the remaining duxelles
Wrap the prosciutto completely around the beef using the plastic wrap tight, form a tight log twisting the ends together. Wrap in another piece of glap wrap if necessary
Place beef into the fridge for at least 30 min or up to 24 hours
Roll out puff pastry on a floured surface. Place the roast in the middle of one sheet of pastry and trim until there is a 3cm border around the beef. Paint this border with egg yolk.
Place the other sheet on top and seal the two sheets together with a fork or the end of a spoon. Trim until there is a 2-3cm border around the roast. Mark the top of the roast with diagonal lines without piercing the pastry.
Roast on a baking tray lined with baking paper (NOT ALFOIL) until it reaches an internal temperature of 48 degrees celcius Let rest for 10 min before carving