3 to 4 lb. center-cut fillet of beef
1 stick plus 1 tbsp. butter
1 tsp. dried thyme
2 to 3 shallots
Salt and pepper
Flour
Dry mustard
Allspice

FOR THE SAUCE:

1/2 c. dry red wine
2 c. canned beef broth
6 tbsp. Madeira
1 tbsp. arrowroot (can use cornstarch or flour)
2 tbsp. dijon mustard

Trim fillet of all fat and silverskin membrane beneath the fat. Reserve some trimmings. Using a paring knife, make a tunnel for the stuffing through the center of the meat. The easiest way is to make a tunnel from each side to meet in the middle. Put a finger through each hole to make sure there is a continuous tunnel.

Bring the butter to room temperature. Mince the thyme and shallot. Melt 1 tbsp. butter and saute thyme and shallots over low heat until soft, about 1 minute. Cool slightly. In a small bowl, combine the remaining butter, thyme-shallot mixture, and plenty of salt and pepper. Put the butter into a pastry bag with a plain pastry tube. Pipe the butter into the holes on each side of the roast. Alternatively, you can shape the butter into a thin cylinder, chill, and insert into the tunnel. Plug the ends of the tunnel with small meat trimmings and tie the roast to secure the trimmings.

Coat the roast with oil. Sprinkle the roast with a mixture of flour, salt, pepper, dry mustard, and allspice. Carefully put the roast into the heated pan and sear in a preheated 500 degree oven for 10 minutes. Lower the heat to 350 degrees and roast until internal temperature is 125 degrees for medium rare. (A general rule is to roast for about 13 minutes per pound.) Let roast rest at least 20 minutes before carving.

While roast is resting prepare the sauce. Skim any fat from the pan juices. Add the red wine and deglaze the pan over moderately high heat, scraping the brown bits. Boil the liquid until reduced by half. Transfer to a saucepan. Add the broth and 1/4 cup Madeira and boil for 5 minutes.

In a small bowl, stir together the remaining Madeira, the arrowroot, and the mustard. Add the mixture to the pan in a steady stream, whisking, and boil for 1 minute. Season to taste and transfer to a heated sauceboat.

Carve the roast in thick or thin slices as desired. Place a little sauce on the slices and pass the rest separately.