Preheat the oven to 200°C. Preheat oven to 200°C. Place 7 prosciutto slices in a row, side-by-side and slightly overlapping, to create a rectangle. Repeat with the remaining prosciutto slices, slightly overlapping, at the long side of the first rectangle.
Mix the cashews and pesto together in a small bowl. Spread the pesto mix over the beef. Place the beef, dip-side down, on the prosciutto. Roll up to enclose the beef. Place the beef, seam-side down, in a roasting pan. Roast for 45 minutes for medium or until cooked to your liking. Transfer to a plate. Cover with foil. Set aside for 10 minutes to rest. Top with basil.
Recipe by Chompchomp at http://www.chompchomp.com.au/2012/12/prosciutto-wrapped-beef-fillet-with-pesto/