Season the chicken breasts evenly with kosher salt and freshly ground black pepper on both sides.
Heat the olive oil in a large skillet over medium-high heat until shimmering.
Add the chicken breasts to the skillet and cook for 5 to 6 minutes on each side, or until golden brown and cooked through. Remove the chicken from the skillet and set aside on a plate.
Reduce the heat to medium and add the minced garlic to the skillet. Sauté for about 1 minute until fragrant, stirring frequently to avoid burning.
Pour in the chicken broth, scraping the bottom of the skillet with a wooden spoon to loosen any browned bits.
Add the heavy cream, lemon zest, lemon juice, orange zest, orange juice, and chopped rosemary to the skillet. Stir to combine and bring the mixture to a gentle simmer.
Let the sauce simmer for about 5 minutes, stirring occasionally, until it thickens slightly.
Stir in the unsalted butter until melted and the sauce is smooth.
Return the cooked chicken breasts to the skillet, spooning the creamy citrus rosemary sauce over the top.
Simmer for an additional 2 to 3 minutes to heat the chicken through and meld the flavors.
Remove from heat and serve the creamy citrus chicken garnished with additional fresh rosemary if desired.