Heat the butter in a large skillet over medium-high heat heat. When the butter starts to bubble, sear the tournedos, letting them stick to the pan before you turn them over to an unseared side, until browned all over. Remove the tournedos and keep warm.
Add the brandy to the pan and bring to a boil. Caution: the brandy may flame briefly. Whisk the pan to dissolve the juices as the brandy reduces by about two thirds.
Add garlic, onion, celery, parsley, salt and pepper. Saute until the vegetables are tender. Add the wine, Worcestershire sauce, lemon juice, and soy sauce. Bring to a low boil and simmer until the sauce is thickened enough to coat the back of a spoon. Strain the sauce and return to the pan.
Slice each of the tournedos into four equal slices. Return them to the pan and cook in the sauce for about 30 seconds. Serve with all the sauce that sticks to them, plus a tablespoon more.