This soup, associated with the ancient Lombardian agricultural and university town of Pavia (Albert Einstein once lived there), is utterly simple. I had a particularly good version on day at Il Tastevin, a restaurant in Vigevano, about 15 miles northwest of Pavia, and the proprietor, Maurizio Barone, was kind enough to share his recipe with me. "It is a very 'poor' plate," he wrote when he sent it to me, "and easy to make, but diners like it very much."
Adapted from “The Country Cooking of Italy” by Colman Andrews (to be published in the Fall of 2011 by Chronicle Books).
Meanwhile, melt the butter in a medium skillet over medium-high heat, then quickly fry the bread in batches for 30–40 seconds per side, turning once, until the slices are golden-brown. Put 1 or 2 slices in each of 4 warmed soup plates just large enough to hold them.
Carefully break 1 egg on top of the toast in each plate. Salt the eggs generously, then sprinkle each with 1 tablespoon of the Parmigiano. Pour about 1 cup of broth into each bowl, pouring around the bread, not over the egg and cheese. Keep the broth boiling as you work. (The broth will cook the eggs.) Serve with additional Parmigiano on the side.