Instructions: For the Bernaise Sauce: Combine vinegar, wine, shallots, black pepper, and 1 1/2 teaspoons tarragon in a small saucepan. Cook over medium heat until reduced to 1 tablespoon, 5 to 10 minutes. Add egg yolks and 1 tablespoon water to reduced vinegar mixture. Whisk until thick and pale, about 2 minutes. Set pan over moderately-low heat, and continue to whisk at reasonable speed, reaching all over bottom and insides of pan, where eggs tend to overcook. To moderate heat, frequently move pan off burner for a few seconds, then back on. As they cook, the eggs will become frothy and increase in volume, then thicken. When the bottom of the pan is visible in the streaks left by the whisk, and the eggs are thick and smooth, remove pan from heat.

By spoonfuls, add soft butter, whisking constantly to incorporate each addition. As the emulsion forms, add butter in slightly larger amounts, always whisking until fully absorbed. Continue incorporating butter until sauce has thickened to desired consistency. Season with salt, remaining 1 1/2 teaspoons chopped tarragon and, if desired, pepper. Add a few drops of lemon juice if necessary. (

Makes about 1 cup)

Heat oven to 250 degrees. Stand meat on its wider cut end on a solid work surface. Fold a kitchen towel lengthwise once or twice into a wide band, and drape it loosely around the upright meat like a scarf. Gather the ends of the towel, and twist to form a tight collar that will hold meat in a round shape during pounding; grasp securely in one hand. With the other hand, pound top of meat with a meat mallet until flattened into an oval steak, about 2 inches thick and 5 to 7 inches wide.

Heat a medium grill pan over high heat to very hot. Rub steak with oil, and season with salt and pepper.

Place steak on grill pan at an angle to ridges, and cook until ridges leave clear marks, 2 1/2 to 3 minutes. Turn, maintaining same angle and repeat on second side. Turn again, rotating so visible grill marks are perpendicular to ridges. Cook until a crisscross is clearly marked, 2 1/2 to 3 minutes. Turn once more, maintaining same angle, and grill so second side has been on grill exactly as long as first side. Brown steak on outside edge, holding with tongs or propping against a potato, shifting meat so entire edge gets browned. Grill a total of 10 to 12 minutes, depending on thickness of steak and desired degree of doneness.

Meat will be barely springy to the touch, indicating that it is still rare. Transfer to a small shallow roasting pan, and place pan in oven for 15 minutes. Remove to a cutting board; slice thin on a bias. Place on a warm serving platter, and pour pan juices over. Serve with bearnaise sauce on the side.

This recipe yields 4 servings.

NOTES : Julia Child and Jacques Pepin co-authored "Julia and Jacques Cooking at Home" (Knopf, 1999; $40)

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