Peel the apples, cut into 1 mm dice and place in iced water to prevent browning.
Sift the flour into a bowl and, using a wooden spoon, mix in the yeast, egg, marsala, mineral water, olive oil and caster sugar. Cover and set aside for at least 20 minutes. Drain the apple, pat dry and stir through the batter.
Heat oil for deep-frying in a large heavy-based saucepan or deep-fryer u