Preheat oven to 190 degrees C (375 degrees F). Line three jelly roll tins with parchment paper. Prepare a pastry bag with a size 6 tip (1.5cm).
Separate the eggs. Whisk the egg yolks with 1/2 of the sugar and all of the vanilla. Beat until very light coloured. This will take about 5 minutes.
In a clean bowl beat the egg whites until they hold soft peeks. While beating, slowly add the salt and the remaining sugar until combined. Gently fold the beaten egg whites into the egg yolk mixture.
Sift the flour over the egg mixture and gently fold it in.
Fill the pastry with half of the batter and pipe 9cm fingers, 4cm apart, in rows on the parchment paper. Continue with the second half of the batter in the same manner.
Bake at 190 degrees C (375 degrees F) for about 15 minutes until firm to the touch and golden. Remove the paper and fingers from the baking tray and place on racks to cool. After cooling, remove fingers from the paper and use, or store between layers of wax paper in a airtight container. These freeze well.