Season both sides of the chicken with salt and pepper to taste.
Over medium high heat, melt butter and add 1 tablespoon olive oil
Pan-sear the chicken breasts until browned on one side, about 5 minutes.
Lower heat to medium and flip the chicken to the other side. Cover and continue cooking for 10 minutes .
Remove chicken from skillet and let it rest.
Add the remaining 1 tablespoon olive oil to the same skillet, and saute the mushrooms, Lemon zest, Red pepper flakes and garlic for 2 minutes.
leave skillet over medium-high heat and pour 1 1/4 cups of the chicken broth into skillet (the chicken skillet), add the Creamy. Bring to a boil, then reduce to medium-low and let simmer until reduced by about 1/2, about 4 - 5 minutes.
Whisk together remaining 1 Tbsp chicken broth with cornstarch. Pour into chicken broth mixture in skillet and allow to gently boil, while whisking constantly, 1 minute.
season with pepper to taste and a little salt if needed, then return return chicken to skillet.
Let the chicken cook for another 5-8 minutes or so until it's cooked through and the sauce has thickened a bit.
Garnish with parsley, rosemary.