In a bowl combine flour, sugar and ½ tsp salt. Add butter and, using fingers, rub in until mixture resembles breadcrumbs. Whisk together egg and ¼ cup water and stir through flour mixture. Gently knead dough to combine, wrap in plastic wrap and refrigerate for 1 hour.
For filling, press ricotta through a sieve into a bowl, add remaining ingredients and combine.
Divide dough into 4 pieces and, using a pasta machine, roll dough, starting at the widest setting and gradually reduce setting by a notch after each roll until dough is 5mm thick.
Place teaspoonfuls of ricotta at 5cm intervals along the bottom edge of each pastry sheet. Brush eggwhite around each spoonful, fold top half over filling to enclose, then using a fluted 5cm cutter (see note) cut into squares. Repeat with remaining pastry and filling. Place on baking paper-lined trays and stand for at least 2 hours.
Heat oil in a deep-fryer, or large, deep saucepan to 180C, add 4 ravioli and fry for 2 minutes or until golden brown. Remove with a slotted spoon and drain on an absorbent paper-lined plate. Repeat with remaining ravioli. Serve warm, dusted with icing sugar.
Note Fluted square cutters are available from
specialty kitchenware stores.