Sear the Chicken: Heat a large skillet over medium-high heat and add the olive oil. Season the chicken thighs with salt and black pepper. Place them in the skillet and sear for 2-3 minutes on each side until browned. Remove the chicken from the skillet and set aside.
Sauté the Aromatics: In the same skillet, add the minced garlic, Italian seasoning, oregano, red pepper flakes, and sun-dried tomatoes. Sauté for 2-3 minutes until fragrant.
Make the Sauce: Pour in the chicken stock and heavy cream and add the grated Parmesan. Stir well. Dissolve the cornstarch in a small amount of water and whisk it into the sauce to help thicken it.
Simmer the Chicken: Return the chicken thighs to the skillet, covering them with the sauce. Lower the heat to a simmer and cover the skillet with a lid. Let the chicken cook for 15-20 minutes, or until fully cooked, stirring occasionally to prevent the sauce from sticking to the pan.
Finish and Serve: Once the chicken is cooked through, stir in the fresh basil leaves and remove the skillet from the heat. Serve warm, spooning the creamy sauce over each chicken thigh. For extra flavor, garnish with more Parmesan, sun-dried tomatoes, and fresh basil.