Spray a sheet of filo with oil then cut into 4 even rectangles. Place a piece of prosciutto on a short side of each rectangle. Place an asparagus spear on top of each, leaving the tip beyond the end of the pastry
Sprinkle each with some Parmesan then roll up. Place on a paper lined baking tray. Repeat with remaining ingredients. Spray the top of each straw with oil and sprinkle with more Parmesan
Bake in a very hot oven 220°C for 10 minutes or until golden brown and cooked through in the centre