Melt the margarine in a large pan and cook the onion until soft. Add mince and brown evenly, then add the breadcrumbs and lemon juice. Adjust the seasoning.

Sift the flour and curry powder into a bowl. Stir in the oil and enough cold water to bind to a firm but manageable dough.

Roll out the dough on a lightly floured surface to a rectangle 25 x 33 cm (10 X 13 inches). Trim the edges. Spread with mustard to within 2.5 cm (1 inch) of the edge and sprinkle with the cheese.

Spoon the savoury mixture down the centre. Dampen the edges and bring each edge over the filling. Seal.

Place seam-side down on a baking sheet. Roll out the trimmings and cut strips to garnish. Brush pastry with milk, arrange the decorative strips, reglaze and sprinkle with sesame seeds. Cut a slit on top and bake at 190°C (375°F) mark 5 for about 30 minutes.