Once the flames are completely out, turn the heat back to medium-low. Add the crème fraîche, chicken stock, heavy cream, dijon mustard, fresh thyme, and green pepper. Whisk everything together, scraping up the browned bits (fond) stuck to the bottom of the pan.
½ cup creme fraiche, ½ cup chicken stock, 2 Tablespoons heavy cream, ½ teaspoon Dijon mustard, 1 teaspoon fresh chopped thyme, 1 teaspoon ground green peppercorns