Mix all the ingredients for the dough into a warm dough that is pleasant to the touch. Roll into a pastry 1cm. thick and cut out rectangles 15*5cm in size.
Spoon potato puree into each pastry piece,
and pinch it closed. Seal well on all sides, and place onto a lined baking pan with the sealed edge face down (to prevent it opening during baking).
Brush the bourekas with the egg glaze, and sprinkle sesame/nigella on top.
Bake at 180C in a pre-heated oven for approx. 20 minutes until golden brown.