Sift the flour and salt into a mixing bowl. Add the butter and lard in walnut-sized pieces, then add the water.

Press the dough gently together with floured hands, then roll out on a well-floured board into a long thin oblong shape with a floured rolling-pin, keeping the edges as straight as possible with a palette knife. Fold this oblong strip into three with the open edge facing you.

Turn the dough a quarter turn clockwise, and roll out to an oblong shape again. Repeat this folding and rolling process three times more, turning the dough a quarter turn each time it is folded.

Fold into three, wrap in polythene or foil and chill in the refrigerator for 30 minutes.

Roll out the chilled dough very thinly into a square shape. Cut into 12 x 10 cm (4 in) squares. Put 2 tsp jam in one corner of each square of dough, leaving a margin.

Dampen the edges with water. Fold the dough over the jam to form a triangular shape and press the edges together to seal. Brush with a little milk and dredge with caster sugar.

Place on a greased baking sheet. Bake in the oven preheated to fairly hot (200°C/400°F or Gas Mark 6) for 20 minutes or until the pastry is puffed and golden-brown.