Soak the dried porcini in a bowl with 3/4 cup hot water for 30 minutes. Remove the mushrooms with a slotted spoon, chop them finely, and set them aside in a small bowl. Strain the soaking liquid through a coffee filter to remove any grit. (You should have a generous 1/3 cup liquid).
Bring the stock to a full boil with the thyme, sage, bay leaves and mushroom soaking liquid in a medium saucepan, reduce the heat, and keep it at a bare simmer.
Heat the olive oil in a heavy 2 to 3-quart saucepan, and cook the leeks and garlic over moderate heat, stirring frequently with a wooden spoon, until very soft but not browned, about 6 minutes. Add the fresh mushrooms and the anchovies, and cook, stirring constantly, for 5 minutes, or until the mushrooms are softened (reduce the heat slightly if the mushrooms begin to stick). Stir in the rice and cook, stirring constantly, for 2 minutes. Add the wine, and cook, stirring constantly, until the wine is absorbed, about 1 minute. Stir in the chopped dried mushrooms.
Remove the herb sprigs from the stock with a slotted spoon or tongs. Add about 1/2 cup simmering stock to the rice, and cook, stirring constantly, until all the stock is absorbed. Continue adding stock, about 1/2 cup at a time, and cook, stirring constantly and letting each addition be absorbed before adding the next, until the rice is al dente, 20 to 25 minutes; season with salt and pepper about halfway through the cooking.
Remove the pan from the heat and stir in the butter, Parmigiano-Reggiano, and salt and pepper to taste. Garnish risotto with the additional thyme and sage sprigs and serve immediately.