In a bowl, mix the flour with all the other ingredients up to and including the lemon zest. Combine the yoghurt, egg, oil and grappa, mix into the flour, combine to form a soft dough, knead briefly.
Heat the oil to approx. 175°C in a cooking pot. Empty the sugar into a deep dish. With lightly floured hands, shape the dough into approx. 35 balls (approx. 4 cm in diameter). Deep-fry the dough balls in batches for approx. 4 mins. until golden brown, turning occasionally. Remove, drain on kitchen paper, toss in the sugar while still hot.