Preheat oven to 200C.
In a pan heat 2 tbsp oil and fry half the onion. (8 mins)
Add cabbage, season and cook until soft. Set aside to cool.
In a separate pan, fry remaining onion in the rest of the oil. Add mince and water and season.
Mix well, cover and simmer for 30 minutes on low heat, stirring from time to time. Set aside to cool.
Cut pastry into nine squares.
Scoop some of the meat and cabbage fillings onto the middle of each piece, and fold over into rectangles and seal with a little egg.
Arrange pirozhki on a lined baking tray and brush with the remaining egg.
Bake for 20 minutes until golden.