Step 1Add just enough hot water to the dried mushrooms to cover them and soak for 15 minutes. Meanwhile, in a medium saucepan combine the stock and 5 cups water. Bring to a boil, reduce the heat to low and maintain at a low simmer.
Step 2Quarter the fresh mushrooms and saute them with 1 tablespoon butter over medium-high heat in a small skillet until they are lightly browned. Season lightly with salt, reduce heat to medium and cook until the mushrooms have reabsorbed their moisture. Set aside.
Step 3In a large skillet or pot over medium-low heat, melt 3 tablespoons butter, add the minced onion and cook until the onion is soft and fragrant, about 4 to 5 minutes. Do not let the onion brown.
Step 4Drain the soaked mushrooms, adding the liquid to the simmering stock. Chop the mushrooms, add them to the onions along with the sauteed fresh mushrooms and cook until fragrant, 3 to 4 minutes.
Step 5Add the rice and increase the heat to medium. Cook, stirring, until the rice makes a clicking or "singing" sound as it scrapes the bottom of the pan and you can see the outside of the kernel become translucent, about 2 to 3 minutes. Add the wine. Cook, stirring, until it evaporates completely, about 3 minutes.
Step 6Begin adding the simmering stock, between three-quarters and 1 cup at a time. Cook after each addition until the stock has evaporated enough so that you can see the bottom of the pan come clean when you scrape it with a wooden spoon, about 5 minutes. Add the 1 teaspoon salt.
Step 7Repeat, adding more stock each time, until the rice is chewy but tender, with no chalky center. This will take about 20 minutes. Do not stir continuously, just when adding the stock to the pan and when it is nearly dry. You will not use all of the stock.
Step 8While the rice is cooking, chop the pea sprouts lengthwise in roughly half-inch pieces.
Step 9When the rice is done, add another one-half cup stock to loosen the mixture slightly. Remove the pan from the heat. Stir in 2 tablespoons butter and the grated Parmigiano-Reggiano cheese. Stir vigorously to free as much starch as possible, which in combination with the cheese, will thicken the rice and liquid. Taste and season with more salt if necessary. Gently stir in the chopped pea sprouts.
Step 10Spoon the risotto in generous mounds in the centers of heated flat bowls. Serve immediately, passing additional grated Parmigiano for those who want it.