Set the oven to 200C/400F/gas mark 6. Line 2 large bakng sheets with silicone baking paper. Draw parallel lines 12.5cm/5 inches apart on the paper.

Separate 5 of the eggs. beat the yolks with the whole egg and 110g of the caster sugar in a large bowl until they are nearly white.

Whisk the egg whites until stiff and gradually whisk in the remaining caster sugar. Fold the egg whites into the egg-yolk and sugar mixture. Carefully fold in the sifted flour and arrowroot.

Fit a 5mm plain nozzle into a piping bag and fill the bag with the mixture. Pipe 12.5cm fingers between the parallel lines on the baking paper. the fingers should be just touching.

Place in the top of the oven for about 10 minutes or until the sponge has risen and is biscuit-coloured.

Remove them from the oven, invert on to a clean tea towel and immediately and carefully peel off the paper. Turn the sponge fingers on to a wire rack to cool.