Beef in Brunello Wine

To make the sauce: Preheat the oven to 400 F. Chop the beef bones into small pieces and place in a large roasting pan. Roast the bones for an hour, until well browned. Drain off the fat which accumulates. Place the bones in a large stockpot with the carrots, celery, onions, tomatoes, bay leaves, and 2 quarts of the wine. Bring to a boil and skim any foam which rises. Reduce the heat to medium and simmer until the liquid is reduced to about 2 cups. Strain, discarding the solids, and place the pan back on low heat. Separately, combine the shallots, sugar, and 3 tablespoons of the butter in a saute pan. When the shallots begin to brown, add the remaining wine and simmer until the wine has completely evaporated. Add the shallots to the reduced stock and bring to a boil; cook for 5 minutes. Season to taste with salt. Stir in potato flour a little at a time until the sauce thickens. Cut the remaining butter into small pieces. Remove from the heat and add the butter, a few pieces at a time, whisking continuously. Strain again through a fine-meshed sieve. Set aside and keep warm over tepid water, or in an insulated container.

Rub the filets with olive oil. Season on all sides with salt. Heat a large well-seasoned cast iron skillet over high heat, then sear the filets quickly on all sides, including the edges. Reduce heat to medium and cook 5 to 6 minutes for rare, 8 to 10 minutes for medium rare, 13 to 14 minutes for well, turning occasionally to cook evenly. Baste the filets with pan juices as they cook. Lightly sprinkle sea salt on a platter and place the steaks on the salt to rest.

Put the spinach and butter in a large saute pan over medium heat and saute until the spinach is wilted, tossing gently as it cooks. Cook in batch if necessary. Set aside.

To serve: Cut the filets lengthwise into 1/4-inch-thick slices. Mound wilted spinach in the center of each warmed serving plate. Fan beef slices in a circle over the spinach. Spoon Brunello sauce around the beef slices.