Sirloin steak with Périgueux Sauce

Preparation

1. Clean the sirloin thoroughly, season the medallions with salt and pepper and brown them in a drop of oil over a very high heat, turning them over and over again. Cover and set aside.
2. Chop the shallots as finely as possible and poach them in butter until they are tender but not browned.
3. Add the flour and stir for about three minutes.
4. Add the white wine and allow to reduce by half. Add the meat stock and port and reduce again or until the sauce has a texture.
5. Remove from the heat, add the nut butter, stir and finish with grated truffle to taste.
6. Pour the boiling sauce over the tenderloins and serve with mashed potato