Sift flour and castor sugar into a bowl and rub in the margarine until the mixture resembles fine breadcrumbs. Add the water and egg yolk and mix to form firm dough. Turn onto a lightly floured board and knead gently. Set aside in a cool place for 30 minutes.
Roll pastry out thinly and cut out 12 circles. Use these to line a 12 hole muffin tin. Fill with Fruit mince mixture. Brush edges with egg white. Cut Star shapes for tops. Pinch pastry edges together at edges and brush with egg white.
Bake for about 15 minutes at 200c. Sprinkle with castor sugar while still warm.