You will need
Preheat oven to 200C/400F/Gas 6.
Grill the bacon for 2-4 minutes, turning once. Drain on kitchen paper before cutting into small pieces.
Melt 15g/.5oz margarine in a saucepan and saute the onion for 1-2 minutes.
Remove from the heat and mix in the drained spinach, bacon, feta, egg and season well.
Melt the remaining margarine in another pan. Separate 5 sheets of filo pastry and brush each with a little of the melted margarine.
Layer the sheets one on top of another. Cut into 8 squares, approximately 7.5cm/3in, repeat with the remaining pastry.
Lightly grease individual bun tins and line with pastry squares, gently pressing the squares into the bun tins.
Place 5-10ml/1-2tsp of the filling into each case. Carefully separate the five layers of pastry at each corner.
Bake for 10-15 minutes until the pastry is golden. Serve warm.