Knish

Method

1. Beat the 1 egg in a cup. In a bowl whisk together 100 g plain flour, 0.25 tsp baking powder and 0.25 tsp fine salt. Make a well, add half the beaten egg, 1 tbsp sunflower oil and 30 ml lukewarm water, and bring together into a soft, slightly sticky dough. Knead on the worktop for 5 minutes until smooth and elastic, then cover and rest at room temperature for 30 minutes. Cover the remaining egg and keep it for the glaze.
2. Put the 200 g of potato chunks in a small pan, cover with cold well-salted water, bring to the boil and simmer for 20 minutes until a knife slides through easily. Drain thoroughly and return to the dry pan over low heat for 30 seconds to steam off, then mash smooth with no lumps.
3. Meanwhile heat 2 tsp of schmaltz or sunflower oil in a small frying pan over medium-low heat and cook 70 g of finely chopped onion for 12 minutes, stirring often, until soft, sweet and deep golden at the edges. Scrape the onion and all the fat into the mashed potato, season generously with salt and plenty of black pepper — knish filling should taste peppery and forward — and leave until cool enough to handle.