These stuffed buns were brought to New York by immigrants from Eastern Europe in the early 1900s.
320g (11¼oz) potatoes, cut into cubes
1brown onion, finely chopped
3teaspoonsmatzo meal or ordinary breadcrumbs
1egg, beaten (set 2teaspoons aside for glazing)
190g (6¾oz) plain (all purpose) flour
45ml (1½fl oz) water
Place the potatoes in a saucepan of cold water, bring to the boil, then lower the heat and simmer for 20 minutes until they are quite tender. Drain. Meanwhile, sauté the onion in the oil over medium heat for 5–10 minutes until softened and lightly brown. Mash the potatoes and onion with the oil using a fork and incorporate the breadcrumbs, sugar and beaten egg. Season with salt and pepper.
Using a food processor or by hand, mix until until combined.
Shaping and Cooking
Preheat the oven to 180°C (350°F/Gas 4). On a floured surface, roll out the dough into a rectangular shape about 28cm (11¼inches) long and 5mm (¼inch) thick. Spread the filling in a sausage shape along the length of the rectangle, then roll the dough over the sausage and pinch the ends of the tube to close it. With the side of your hand or a chopstick, make six dents along the length of the sausage. Separate the portions using a knife or dough cutter. You obtain seven sections that are open on both sides. Pinch one end closed and reshape the knish so it’s round (it will have been put out of shape by the cutting). Pinch the sides at the other end towards the centre, leaving a small opening (this is the top of the knish). Place the shaped knishes on a baking tray lined with baking paper. Brush the tops with the reserved egg and bake for about 40 minutes until golden brown.