How to Make It
Oil a 9-by-9-inch baking dish. In a medium saucepan, bring the water to a boil. Slowly whisk in the cornmeal and 1 teaspoon of salt and cook over low heat, whisking often, until very creamy and cooked, 30 minutes.
Remove the polenta from the heat and stir in 2 tablespoons of the butter, the truffled pecorino and 2 tablespoons of the Parmigiano-Reggiano. Season with salt and pepper and scrape the polenta into the prepared dish, smoothing the top. Let stand for about 30 seconds, until the polenta firms up slightly and spread the remaining 1 tablespoon of butter on top. Press a piece of plastic wrap directly onto the surface of the polenta and let cool to room temperature.
Preheat the oven to 450°. Uncover the polenta. Sprinkle the remaining 3 tablespoons of Parmigiano over the top and bake for 10 minutes, until hot. Preheat the broiler. Broil the polenta 6 inches from the heat for about 2 minutes, until golden brown and glazed.
The polenta can be prepared through Step 2 and refrigerated overnight. Bring to room temperature before proceeding.