In a large saucepan, heat the stock until barely simmering and keep warm over low heat.
In a large, heavy pot or Dutch oven cook the bacon over medium-low heat, stirring occasionally, until crisp, about 10 minutes. Drain on paper towels. Discard all but 2 Tbs. of the drippings. Increase heat to medium. Add the onion to the pot and cook, stirring occasionally, until softened, about 5 minutes. Add the rice. Cook and stir 1 to 2 minutes, or until rice begins to turn translucent.
Stir in 7 cups of the hot stock and the salt and bring to a boil. Reduce heat, cover, and simmer, stirring once or twice, until rice is almost tender, 13 to 15 minutes. Add the thawed peas. If the rice looks dry, stir in the remaining hot stock, as needed, to reach desired consistency. Cook, stirring, 1 to 2 minutes more or until the risotto looks moist and creamy, and the rice is barely firm in the center. Stir in the cooked bacon, 3/4 cup Parmesan cheese, butter, and lemon juice. Reserve 3 cups risotto for later use. Serve with additional grated Parmesan.
Transfer cooled leftover risotto an airtight container and freeze to use in Baked Arancini.