Season both sides of the chicken breasts with kosher salt and freshly ground black pepper.
Heat olive oil in a large skillet over medium-high heat until shimmering.
Add the chicken breasts to the skillet and cook for 5-6 minutes on each side, or until golden brown and cooked through. Remove chicken from the skillet and set aside on a plate.
Reduce heat to medium and add the minced garlic to the skillet. Sauté for 30 seconds until fragrant, stirring constantly to avoid burning.
Pour in the chicken broth and use a wooden spoon to scrape up any browned bits from the bottom of the skillet.
Add the heavy cream, fresh rosemary, lemon zest, lemon juice, orange zest, orange juice, and Dijon mustard to the skillet. Stir well to combine.
Simmer the sauce for 5-7 minutes, stirring occasionally, until it thickens slightly.
Return the cooked chicken breasts to the skillet, spooning the sauce over the top. Cook for an additional 2-3 minutes to heat through and allow the flavors to meld.
Remove from heat and serve the creamy citrus chicken garnished with additional fresh rosemary if desired.