Gratineed Asparagus and Prosciutto
2 lbs. asparagus
4 T. unsalted butter
2 to 3 oz. thinly sliced prosciutto, cut into small strips
1/2 C. freshly grated Parmigiano-Reggiano
Cut off the tough ends of the asparagus. If the asparagus stalks are thick, peel them with a vegetable peeler or small sharp knife. Rinse the asparagus and arrange it in 1 or 2 bunches, securing them with rubber bands or kitchen string.
Bring 2 to 3 inches of water to a boil in an asparagus cooker or in a narrow stockpot over medium heat. Add a nice pinch of salt and stand the asparagus in the pot. Cover the top of the asparagus loosely with foil or with the cooker lid and cook until tender but still a bit crunchy to the bite (it will finish cooking in the oven), 3 to 8 minutes, depending on the thickness. Place a large bowl of ice water next to the stove. Remove the asparagus from the pot, remove the rubber bands or string, and place in the ice water to stop the cooking. Drain again, place on a clean kitchen towel, and pat dry. (The asparagus can be cooked to this point up to a day ahead. Cover tightly and refrigerate.)
Preheat the oven to 400°F. Smear the bottom of a large baking dish with some of the butter.
Melt the remaining butter. Arrange a layer of the asparagus in the baking dish and season lightly with salt. Drizzle some of the melted butter over the asparagus, scatter the prosciutto over it, and sprinkle lightly with Parmigiano. Arrange another layer of asparagus on top and repeat as above, finishing with a generous sprinkling of cheese.
Place the baking dish on the middle rack of the oven and bake until the cheese has a nice golden color, 6 to 8 minutes. Remove from the oven and let stand for a few minutes before serving.