Before preparing the tenderloins, place the prunes in a large bowl and pour half a glass of hot water over them. Put them aside to soak.
Rinse the tenderloins, dry them and then cut the outer membrane off. Cut the meat into slices about 1 cm thick, then gently pound them. Rub the meat with the olive oil, crushed garlic, salt and pepper.
Place the soaked prunes on either side of each slice of meat, roll each slice in prosciutto and then place in a greased ovenproof dish. Pour the brine from the prunes over the meat.
Bake for about 20 minutes in an oven preheated to 210 degrees.
Heat the cream with finely grated parmesan, mustard and a pinch of salt in a saucepan over a medium heat. Pour into the dish, evenly between the rolls.