Entrecôte à la moutarde ancienne

Sauce

1. 1 In a stainless steel or enameled pan, sauté the grated onion, well drained, in the butter.
2. 2 When the onion starts to color, add the heavy cream and chicken broth and cook over high heat until reduced by almost half.
3. 3 Then, over low heat or even off the heat, add both mustards and mix well. Keep the sauce warm in a water bath.

Beef

1. 4 Take the meat out of the refrigerator 15 minutes before using.
2. 5 Heat a large skillet well, big enough to fit the steaks. Add a little oil and sear well on one side and then the other.
3. 6 Season with salt and pepper only after grilling.

1. 7 Serve with the sauce spooned over the top.