In a medium saucepan, bring the broth to a simmer. Cover the broth and keep hot over low heat.

In a large, heavy saucepan, melt 2 tablespoons of the butter over medium heat. Add the onion and saute until tender, but not brown, about 3 minutes. Add the rice and stir to coat with the butter. Add the wine and simmer until the wine has almost completely evaporated, about 3 minutes. Add 1/2 cup of the simmering broth and stir until almost completely absorbed, about 2 minutes. Continue cooking the rice, adding the broth 1/2 cup at a time, stirring constantly and allowing each addition of broth to absorb before adding the next, until the rice is tender but still firm to the bite and the mixture is creamy, about 20 minutes total. Remove from the heat. Stir in the Parmesan cheese, the remaining tablespoon of butter, and the salt and pepper. Transfer the risotto to a serving bowl and serve immediately.