Soak the dried mushrooms: Soak mushrooms in 2 cups of lukewarm water for half an hour or more.

Make the meatloaf mixture: In a bowl, break up the beef with a fork. In a small bowl, combine the milk and bread, and mash until creamy. Add the milk and bread to the meat along with the onion, Parmesan, prosciutto, garlic, salt, and pepper. Mix thoroughly by hand. Mix in the lightly beaten egg yolk.

Form a loaf shape: Shape meat into a firm, round ball; then roll this into a salami-like loaf about two and a half inches thick. Tap with your palm to drive out any air bubbles. Roll the loaf in the bread crumbs until evenly coated.

Drain and chop the mushrooms: Drain the mushrooms (reserving the soaking water) and rinse them several times in clean, cold water. Chop the mushrooms roughly and set aside. Strain the soaking water through a fine sieve lined with paper towels. Whisk the tomato paste into the soaking liquid and set aside.

Brown the meatloaf: Heat the butter and oil in a Dutch oven or heavy casserole pan just big enough for the meat. Brown the meatloaf on all sides in the pan over medium heat after the butter foam subsides.

Add the wine and reduce: Add the wine. Increase the heat to medium-high. Boil the wine briskly until reduced one half, turning the meatloaf carefully once or twice.

Add the mushrooms and liquid: Turn heat to medium low and add chopped mushrooms. Add the tomato paste mushroom water to the meat and mushrooms.

Cover and cook: Cook at a simmer for 30 minutes, turning the meat once or twice.

Let rest before slicing: Carefully remove meat to a cutting board. Allow it to cool slightly and settle. Cut into slanted slices about ⅜ of an inch thick. If the sauce seems thin, concentrate it by boiling rapidly for a few minutes. Pour a little sauce on a warm serving platter, arrange the meat slices, then cover with the remainder of the sauce.