(Orig. recipe found in the November 1998 issue of Bon Appetit, now "Epicurious.com" -- I make these every year, but I make some [changes, in brackets, hopefully, BOLD].)

3 1/4 pounds russet potatoes, peeled, cut into 1-inch pieces [unpeeled red potatoes, called "dirty" mashed potatoes]
4 large garlic cloves, peeled [cut in half]
1/2 cup (1 stick) butter [unsalted butter]
3 1/2 ounces thinly sliced prosciutto, finely chopped
3/4 teaspoon minced fresh rosemary
3/4 cup (or more) whole milk [heavy Whipping Cream, milk is borrring]
1 cup freshly grated Parmesan cheese (about 3 ounces)

Instead of cooking the potatoes in water, I add the garlic and cook them in chicken broth. Save the water to use at the end instead of adding milk, or whipping cream, to make them the perfect consistency.

Brown the prosciutto, remove it from the pan (don't clean it), and add the fresh rosemary. Just cook this a few minutes, it gets awesomely aromatic.

Put the cooked potatoes in a really big bowl and fork-mash them. Add the Prosciutto, cooked rosemary (including the pan drippings), butter, and whipping cream. Beat the crap out of them, adding potato water to make them the perfect consistency.

Add the Parmesan cheese, stir it in, and cover to keep warm. (I usually stick it in the warm oven after everything's done. Top with additional sprigs of rosemary.

The next day, if there are leftovers, add egg & flour to make the BEST potato pancakes EV-VER!
Additional fresh rosemary