In a large fry pan heat the clarified butter or olive oil over medium-high heat. Season the chicken breasts with salt and pepper. Saute chicken until golden brown on each side. Remove from pan and set aside.
In the same pan add butter, then sun-dried tomatoes, stirring for a minute. Add tomato paste, and cook for a minute to caramelize the paste slightly. Add the garlic, oregano, chili flakes and lemon zest, stirring , until garlic is fragrant, about 30 seconds. Add the chicken stock to deglaze the pan. Add the chopped basil and spinach leaves, allowing them to wilt in the sauce.
Pour in the heavy cream and bring to a gentle simmer. Add parmesan cheese and stir until melted and sauce thickens. Add dijon mustard, stirring to combine.
Return chicken to the skillet, spooning the sauce over the pieces. Let simmer gently for 5 minutes, allowing the chicken to finish cooking and absorb the flavors of the sauce.
Serve over pasta, rice or potatoes.
Enjoy!