01 - Evenly season the chicken breasts on both sides with kosher salt and freshly ground black pepper.
02 - In a large, deep skillet or Dutch oven, heat the olive oil over medium-high heat. Place the seasoned chicken breasts in the hot skillet and sear for 3-4 minutes per side until golden brown. Remove the chicken from the skillet and set aside on a plate. It will finish cooking in the sauce.
03 - Reduce the heat to medium. Add the minced garlic and finely chopped onion to the same skillet. Sauté for 2-3 minutes until the aromatics are softened and fragrant.
04 - Stir in the sliced sun-dried tomatoes and cook for an additional 1 minute.
05 - Pour in the chicken broth, scraping the bottom of the skillet with a spoon to loosen any browned bits. Bring the liquid to a simmer.
06 - Add the heavy cream, grated Parmesan cheese, dried Italian herbs, and crushed red pepper flakes (if using) to the skillet. Stir thoroughly to combine and bring the sauce back to a gentle simmer.
07 - Add the chopped fresh kale to the simmering sauce. Cook for 2-3 minutes, stirring occasionally, until the kale has wilted.
08 - Return the seared chicken breasts along with any accumulated juices back into the skillet with the sauce and kale. Simmer uncovered for 8-10 minutes, or until the chicken is cooked through (internal temperature reaches 165°F or 74°C) and the sauce has thickened to your desired consistency.
09 - Taste the sauce and adjust seasonings if necessary. Serve immediately, spooning the creamy sauce and vegetables over the chicken.