Preheat the oven to 350 degrees F. Grease and flour 2 baking sheets with 2 tablespoons butter and 2 tablespoons of flour. Mark parallel lines in the flour across the width of the tray about 4 inches apart. Put the eggs and sugar in a large mixing bowl, and beat with an electric mixer on medium-high speed until the mixture is pale yellow, thick, and has tripled in volume, about 8 minutes. Add the egg whites, the remaining 3/4 cup flour, the salt and vanilla, and fold to mix well until the mixture is smooth. Fill a large pastry bag with a 3/4-inch plain tube with the mixture. Pipe fingers about 4 1/2-inches in length on to the baking sheet, using the lines as a guide. Dust the ladyfingers with powdered sugar. Bake until just firm on the outside and soft in the center, 15 to 18 minutes.
Yield: 24 ladyfingers