How to Make It
In a large heatproof measuring cup, soak the porcini in the boiling water until softened, about 15 minutes. Reserve the mushrooms and their soaking liquid separately. In a small bowl, mix the mascarpone with 1/4 cup of Parmesan and the garlic.
Meanwhile, in a medium saucepan, bring the chicken stock to a boil. Cover the stock and keep at a gentle simmer over low heat.
Heat the olive oil in a large saucepan. Add the scallions, bacon and rosemary and cook over moderate heat, stirring, for 5 minutes. Stir in the rice until coated with the oil. Add the wine and boil until almost evaporated, about 2 minutes. Pour in the mushroom soaking liquid, stopping when you reach the grit at the bottom of the measuring cup. Add 1 cup of the stock and cook over moderate heat, stirring constantly, until absorbed. Continue adding stock, 1 cup at a time, stirring until absorbed. The risotto is done when it is creamy and the rice is al dente, about 25 minutes total cooking time. Stir in the mascarpone and the porcini. Season the risotto with salt and pepper.
Melt the butter in a medium skillet. Add the ham; toss over moderate heat until warm. Spoon the risotto into bowls, top with the ham, sprinkle with the parsley and serve with the remaining 1/4 cup of Parmesan.