250 ml(1 cup) extra-virgin olive oil250 mlfino sherry185 gm(1¼ cups) each of plain and self-raising flour1egg, lightly beatenFor deep-frying:vegetable oilSalt cod filling1Sebago potato (about 400gm)750 gmsalt cod, cut into 5cm-thick pieces, soaked in cold water for 36 hours, changing water 4 times, drained1½ tbspolive oil1large onion, finely chopped300 mlpouring cream2 tbspfinely chopped flat-leaf parsley1garlic clove, thinly sliced½ tspdried chilli flakes
For salt cod filling, cover potato with enough cold water in a saucepan. Bring to boil and cook over high heat until potato is soft (20-30 minutes). Drain, peel and mash. Remove skin and bones from salt cod and discard. Set cod aside. Heat olive oil in a saucepan over medium heat, add onion and cook until soft and golden (6-8 minutes). Add cream, parsley, garlic, chilli and salt cod and simmer, stirring occasionally to break down salt cod, until cream is reduced by two-thirds (10-12 minutes). Add potato and mix to a coarse paste. Season to taste with freshly ground black pepper, then cover with plastic wrap and refrigerate until required.
Combine extra-virgin olive oil, sherry, flours and a pinch of fine sea salt in a bowl, turn onto a lightly floured surface and knead until smooth. If dough is too sticky, add extra flour. Cover with plastic wrap and stand for 30 minutes at room temperature.
On a lightly floured surface and, working with one 50gm piece of dough at a time, roll to a 5mm-thick round. Place a heaped tablespoon of salt cod mixture in the centre. Brush edges with beaten egg, fold pastry over filling to form a semi-circle, then pleat edges in one direction to seal. Place on a lightly floured tray and repeat with remaining dough and salt cod mixture (you may have some salt cod mixture remaining).
Preheat vegetable oil in a deep-fryer or deep saucepan to 190C. Add 4 pastries, cook until golden (4-6 minutes), drain on absorbent paper, then repeat in batches with remaining pastries. Serve immediately.