01 -
Pat chicken dry and make a pocket in each chicken breast by slicing horizontally without going all the way through. Season both sides of the breasts and the inside of the pockets with salt and pepper.
02 -
Divide the brie slices between the two pockets, stuffing them inside along with 3-4 apple slices. Optionally, seal the pockets with toothpicks.
03 -
In a large skillet over medium-high heat, heat olive oil and butter. Add the chicken and sear until well browned on both sides, about 2 minutes per side. Transfer to a plate and cover.
04 -
Return the pan to medium heat. Add onions and cook for 2-3 minutes until softened. Add remaining apple slices, season with a pinch of salt, and cook until lightly browned, about 2 minutes.
05 -
Add the wine to deglaze the pan, scraping up browned bits with a spoon. Reduce the wine by half.
06 -
Sprinkle flour over the apples and onions, stirring until no white streaks remain. Stir in chicken broth, maple syrup, cider vinegar, mustard, and rosemary. Bring to a boil, then reduce to low and simmer for 5 minutes. Season to taste.
07 -
Add the chicken back to the pan with its juices. Cover and simmer until the chicken is cooked through, about 8-10 minutes. Chicken should reach 165F. Remove rosemary sprigs and serve.