How to Make It
Preheat the broiler. Arrange the pancetta slices on a baking sheet in a single layer and broil for 1 to 2 minutes, or until golden and sizzling. Drain on paper towels, then crumble.
In a large nonstick skillet, heat the oil. Add the mushrooms, season with salt and cook over high heat, stirring, just until they exude their juices, 3 to 4 minutes. Transfer the mushrooms and their liquid to a strainer set over a bowl and press lightly on the mushrooms; reserve the liquid. Wipe out the skillet and add 1 tablespoon of the butter. Return the mushrooms to the skillet and cook, stirring, until tender and just beginning to brown, about 3 minutes. Add the parsley, cover and keep warm.
In a medium saucepan, combine the stock with the reserved mushroom liquid and bring to a simmer, then keep warm over low heat. In a large, deep nonstick skillet, melt 1 tablespoon of the butter. Add the garlic and cook over moderate heat until fragrant. Add the shallot and cook until softened but not browned, 3 to 4 minutes; discard the garlic. Add the rice and stir until the grains are thoroughly coated with butter.
Add 1 cup of the hot stock to the pan and cook, stirring constantly, until the rice has absorbed most of the stock, 1 to 2 minutes. Continue to cook the risotto, adding the stock 1 cup at a time, and stirring constantly between additions until it is absorbed. Cook the risotto until it has a creamy, porridgelike consistency, about 20 minutes.
Remove the risotto from the heat and stir in the grated Parmigiano-Reggiano, the cream and the remaining 1 tablespoon of butter. Season with salt and white pepper and transfer to warm soup plates. Garnish with the mushrooms, pancetta and shavings of Parmigiano-Reggiano. Serve immediately.