In a large saute pan over medium high heat, add butter. Once melted add garlic and onions and cook for 3 minutes.
Add rice and toast for 3 minutes. Reduce heat to medium. Stir in 1 cup of broth. Stir occasional while broth is absorbed. Once broth is absorbed, add another cup of broth. Repeat until all broth is added and absorbed. Stir in parsley.
Stir in balsamic vinegar and let cook for 3 minutes. Then stir in parmesan cheese and let cook another 3 minutes.