While the chicken is baking, prepare the sauce. In the same skillet used for searing the chicken (over medium heat), add a bit more butter and the minced garlic. Sauté for about 1 minute until fragrant.
Pour in the chicken broth and heavy cream, scraping up any browned bits from the bottom of the pan. Bring to a simmer.
Stir in the grated Parmesan cheese and continue to simmer until the sauce thickens slightly, about 3-5 minutes. Season with salt and pepper to taste.