Sift together the flour, sugar and salt into a large bowl.

Form a well in the centre and add the egg yolk.

Stir to combine then add the milk and butter.

Beat with a wire whisk until the batter is smooth and lump-free.

Add the egg white to a clean and dry bowl, then beat until stiff.

Gently fold into the batter along with the lime zest.

Peel the bananas and cut into slices.

Heat the oil in a pan. When hot dip the banana slices in the batter and immediately drop into the hot oil.

Fry until nicely browned and heated through.

Remove with a slotted spoon and drain on kitchen paper as you cook the next batch.

Serve hot, dusted with icing sugar.