Yield: 12 servings
Wash hands. Wash all fresh produce under cool, running water. Drain well. Heat the heat sauté pan with a splash of olive oil season meat and sear on all edges. Preheat the oven to 400°F. Heat the butter in a 10″ skillet over medium-high heat. Add the mushrooms, salt, pepper, garlic, thyme and onion and cook until the mushrooms are tender and all the liquid is evaporated, stirring often.
Place a large piece of cling film on a clean surface. Lay the Prosciutto slices on top, overlapping them slightly, to form a rough rectangle large enough to cover the beef, making sure there are no gaps. Spread the mushroom mixture on top, leaving a little gap along the edges. Place beef on the on the mushroom prosciutto sheet and roll tightly and refrigerate for 30 minutes.
Sprinkle the work surface with the flour. Unfold the pastry sheet on the work surface. Roll the pastry sheet into a rectangle 4″ longer and 6″ wider than the beef. Brush the pastry sheet with the egg mixture. Spoon the mushroom mixture onto the pastry sheet to within 1″ of the edge. Place the beef in the center of the mushroom mixture. Fold the pastry over the beef and press to seal. Place seam-side down onto a baking sheet. Tuck the ends under to seal. Brush the pastry with the egg mixture. Bake for 25 minutes or until the pastry is golden brown and an instant-read thermometer inserted into the beef reads 140°F. CCP: Final internal cooking temperature must reach a minimum of 165°F, held for a minimum of 15 seconds. CCP: Product must be cooled to a maximum internal temperature of 41°F or less, within 4 hours.