Season the tournedos on both sides with the salt. Brush steaks with the mustard. Spread the pepper on a plate, coat steaks in pepper. Heat the oil in a heavy ovenproof nonstick skillet over medium-high heat. Add the meat and sear for 2 1/2 minutes on each side for medium-rare. Off the heat, sprinkle steaks with brandy. Return the pan to the heat, and flambe. (Depending upon the thickness of the meat, the cooking time of the steaks may vary.)
Sauce au Poivre: Place the black pepper in a dry small saucepan and toast over medium-high heat until fragrant, 1 to 2 minutes. Add the oil and stir to combine. Add the shallots and green peppercorns, and cook, stirring, for 30 seconds. Remove the pan from the heat, add the brandy, return to the heat to flambe, then simmer until reduced by three-quarters. Add the mustard and stir to combine, then add the veal reduction and bring to a boil. Reduce the heat to medium-low and simmer until reduced by half, 10 to 12 minutes. Remove from the heat and add the salt. Serve hot.
Place 3 tournedos on each serving plate. Drizzle with the sauce and serve with the herb-roasted potatoes.
Preheat the oven to 375 degrees F.
Place the bones in a large roasting pan and toss with the oil. Roast, turning occasionally, until golden brown, about 1 hour.
Remove from the oven and spread the onions, carrots, celery, and garlic over the bones. Smear the tomato paste over the vegetables and return the pan to the oven. Roast for another 45 minutes. Remove from the oven and pour off the fat from the pan.
Transfer the bones and vegetables to a large stockpot. Do not discard the juices in the roasting pan. Add the water, bay leaves, thyme, salt, and peppercorns to the stockpot and bring to a boil.
Meanwhile, place the roasting pan over 2 burners on medium-high heat. Add the wine and stir with a heavy wooden spoon to deglaze and dislodge any browned bits clinging to the bottom of the pan. Add the contents to the stockpot. When the liquid returns to a boil, reduce the heat to low and simmer, uncovered, for 8 hours, skimming occasionally to remove any foam that rises to the surface.
Ladle through a fine-mesh strainer into a large clean pot. Bring to a boil, reduce to a gentle boil, and cook, uncovered, until reduced to 6 cups in volume, about 1 hour. Let cool, then cover and refrigerate overnight.
Remove any congealed fat from the surface of the stock. The stock can be stored, covered, in the refrigerator for up to 3 days, or frozen in airtight containers for up to 2 months.
Preheat the oven to 400 degrees F.
Combine all the ingredients in a large bowl and toss to mix well. Transfer to a roasting pan and roast until the potatoes are fork tender, 30 to 40 minutes. Serve immediately.