- 4 teaspoons extra-virgin olive oil, divided
- 1 1/2 cups thinly sliced red onion
- 2 teaspoons minced fresh rosemary, divided
- 1/8 teaspoon salt
- Freshly ground pepper to taste
- 2/3 cup shredded fontina cheese, preferably aged
- 4 (4 ounce) boneless, skinless chicken breasts, trimmed of fat
- 1/2 cup white wine
- 1 cup reduced sodium chicken broth
- 4 teaspoons all-purpose flour
- Heat 2 teaspoons oil in a large nonstick skillet over medium-high heat. Add onion and 1 teaspoon rosemary; cook, stirring occasionally, until the onion is golden brown, 6 to 7 minutes. Season with salt and pepper. Let cool; stir in fontina.
- Meanwhile, cut a horizontal slit along the thin, long edge of each chicken breast half, nearly through to the opposite side. Stuff each breast with 1/4 cup of the onion-cheese mixture.
- Heat the remaining 2 teaspoons oil in the same skillet over medium-high heat. Add the chicken and cook until golden, about 5 minutes per side. Transfer to a plate and cover with foil to keep warm.
- Add wine and the remaining 1 teaspoon rosemary to the pan. Cook over medium-high heat for 2 minutes. Whisk broth and flour in a bowl until smooth; add to the pan, reduce heat to low and whisk until the sauce thickens, about 1 minute. Return the chicken to the pan and coat with the sauce. Cook, covered, until the chicken is just cooked through, 2 to 4 minutes. Serve the chicken topped with the sauce.