1.2 kg rib eye fillet
Bordelaise Sauce1 small shallot finely diced
Trim fillet into an even sized log, rub with olive oil & salt, tie with string and sear in a hot pan until browned & crusted. Rest the meat for a few minutes to cool & remove string. Using the same pan, fry ingredients from butter to thyme until browned and nearly all the moisture has evaporated. Season with salt & pepper to taste. Set aside to cool. On a large sheet of cling film, arrange & overlap prosciutto into a rectangle. Spread mushroom mixture over prosciutto then spread the pate over. Place fillet on the prosciutto, use the cling film to help wrap around the fillet into a tight log, cool in the fridge for an hour to firm up. Join pastry into another rectangle. Remove cling film, place fillet onto pastry and roll the pastry around the fillet until fully covered, join the edges with some water. Tuck the pastry under at both ends of the fillet, trim off any excess pastry. Place onto a baking tray lined with baking paper, with the sealed edges facing down. Brush all over with egg yolk. Chill for an hour then bake in a preheated 180C oven for about 45 mins. Pastry should be golden brown, beef medium rare with an internal temp of about 55C. If temp is less, cook for a bit longer. Note beef will continue to cook for a few mins after you remove it from the oven. Rest for 20-30 mins before carving into thick slices. Put meat juices that 'run out in the sauce.
Fry shallot, garlic and beef trimmings in a saucepan with some butter or olive oil until well browned. Deglaze pan with the wine, cook off the alcohol for a minute then add the beef stock and thyme stalks. Simmer until sauce is reduced by half then strain into another saucepan and bring to a simmer, reduce the heat to low, gradually whisk in frozen butter to thicken (note freezing the butter helps it emulsify into the liquid and thicken the sauce). Whisk in truffle butter. Season sauce to taste. Keep warm but do not bring to a boil again.