Preheat the oven to 350 degrees. 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 with an electric mixer fitted with a wire whisk beat on medium−high speed until the mixture is pale yellow, thick, and has tripled in volume, about 8 minutes, using the mixer.
Add the egg whites, remaining 3/4 cup flour, salt and vanilla, fold to mix thoroughly so 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 lady fingers with powdered sugar.
Bake for 15 to 18 minutes, or until just firm on the outside and soft in the center.