In a saucepan, heat the stock and keep warm, on low flame. In a large skillet, over medium heat, sauté the onion in the butter until translucent or lightly golden brown. Add the rice and stir together until opaque and lightly toasted. Add the wine and a ladleful of the hot stock. Continue to cook and stir with a fork until the liquid is almost fully absorbed. Add 1 teaspoon of salt. As the liquid absorbs, add more stock, a ladleful at a time, waiting until almost completely absorbed before adding more. Add the bay leaf. Cook until rice is al dente and creamy, but not mushy, about 15 minutes. Remove the bay leaf and mix in the Parmigiano. Be careful not to overcook the rice. Serve immediately with a sprinkle of Parmigiano and black pepper.