Place the butter and sugar in a 22 cm (9 inch) fixed-bottomed cake tin. Place over a moderate heat and cook, stirring continuously, for about 5 minutes until golden.
Stuff a little marzipan into the cavity of each pear half, then carefully arrange them cut-side up in the tin.
Roll out the pastry on a lightly floured surface to the size of the tin, then place over the top of the pears and press down all around them. Bake in a preheated oven, 190°C (375°F), Gas Mark 5, for about 40 minutes until the pastry is golden and the juices are bubbling.
Cool in the tin for 10 minutes, then invert on to a large plate and serve with a little ice cream.