2½ cups plain flour
1 teaspoon sea salt
½ teaspoon baking powder
½ cup vegetable oil
½ cup water
1½ teaspoons white wine vinegar
600 grams Agria potatoes, peeled and roughly chopped
2 cloves garlic, peeled
1 tablespoon olive oil
1 tablespoon butter
1 large onion, diced
2 cloves garlic, crushed
1 teaspoon finely chopped rosemary or thyme
½ cup freshly grated Parmesan
50 grams soft feta cheese, crumbled
2 tablespoons finely chopped flat-leaf parsley
sea salt and freshly ground pepper
1 egg, beaten
2 tablespoons sesame seeds
Dough: Put the flour, salt and baking powder in a large bowl. Whisk the oil, water, vinegar and egg in another bowl then pour onto the flour. Mix to a soft dough then tip onto a lightly floured bench and knead lightly until smooth. Form into a disc and wrap in plastic wrap. Set aside for at least 1 hour on the bench or refrigerate for up to 2 days.
Filling: Cook the potatoes and garlic in boiling salted water until tender. Drain and tip back into the saucepan. Put over a low heat for 1–2 minutes and break up roughly with a fork, but leave them a little chunky. This helps drive off excess moisture. Cool.
Heat the oil and butter in a large sauté pan and add the onion, garlic and rosemary with a good pinch of salt. Cover and cook for 15 minutes, stirring occasionally. Uncover and cook for another 10 minutes or until the onions are golden and very tender. Cool.
Put the potatoes, onions, Parmesan, feta and parsley in a bowl and stir together, keeping it a little chunky. Season if needed.
To assemble: Divide the dough into 2 equal pieces. Roll out to 40cm x 25cm rectangles. Place half the filling in a long sausage shape along the edge of the longest side, about 3cm up. Pull the pastry up over the filling then roll (not too tightly) into a log.
Cut the log into 6 equal pieces. Pinch the pastry together at one end to seal then place open end up on the bench. Lightly flatten each one then use your finger to gently push the pastry into the centre of the knish to form a doughnut shape, but without the hole. (This stops the filling from puffing up when cooking.)
Place on a lined baking tray and brush the knish with egg wash and sprinkle with sesame seeds.
Bake for 25 minutes until golden, turning the tray for even browning. Cool for at least 10 minutes as the filling is molten hot! Serve with hot mustard if desired. Makes 12