Salt and pepper the steaks and sear them in the clarified butter for approx. 4 minutes on both sides, remove and keep warm. Fry the parsley root and leek in the remaining fat until they have turned color. Then deglaze with the cognac and let it boil down briefly. Top up with the cream and add the tarragon. Simmer briefly. Then season to taste with pepper and salt, thicken the sauce if you like and pour through a fine sieve before serving.