Make the pastry by mixing the flour into the margarine until it resembles a crumble mixture. Gradually add enough water until it forms a ball of dough. Cover and allow to rest for 20 minutes in a cool area.
Press the dough into a shallow tin and chill for 10 minutes. Prick the base with a fork.
For the viennese topping; beat the margarine, cornflour and icing sugar until light and fluffy. Gradually add the plain flour to form a smooth paste.
Spread the jam evenly amongst the tins.
Place the viennese topping into a piping bag with a star nozzle. Pipe over the jam in a neat pattern of your own choice.
Bake in the preheated oven for 25-30 minutes until lightly golden. Leave to cool, cut into pieces and serve.