In a medium saucepan, bring the broth to a simmer and keep warm over low heat. In a separate medium saucepan, melt 2 tablespoons of the butter over medium heat. Add the onion and garlic and cook, stirring with a wooden spoon, until the onion is transparent, about 5 minutes. Add the rice and cook, stirring, until it is well coated with the butter and starts to turn translucent, about 2 minutes. Add the wine and simmer gently until all the liquid is absorbed, 3 to 5 minutes. Ladle 1/2 cup of the warm broth into the rice mixture and simmer, stirring occasionally, until the broth is absorbed. Repeat, adding 1/2 cup of broth at a time, until the rice is cooked through but still firm, 20 to 25 minutes total. Add the remaining butter and the salt, pepper, and 1/2 cup of Parmesan. Stir to incorporate. Adjust seasoning with more salt to taste. Serve immediately, topping with additional Parmesan.