On a lightly floured worksurface, roll the first disc of pastry into a large rectangle about 30cm x 50cm. Cut the dough in two, vertically, to make 2 long rectangles and cut each horizontally into 3 small rectangles. Put these pieces of dough onto the baking tray lined with baking paper. Divide the filling between the pieces of dough, leaving a border of 1cm around the edges and top with the mozzarella. Roll out the second disc, as before. Brush the edge of each hand pie with a little water and place a second piece of dough onto the filling, gently pressing the edges together with a fork to seal. Chill for 30 minutes until firm.