Preheat the oven to 170 ⁰C, gas mark 3 and have ready a 20-21 cm loose bottomed cake tin.
Combine the biscuit crumbs and melted butter and press firmly into the base of the cake tin.
Beat together the Philadelphia, soured cream, eggs and sugar until smooth. Then add the flour, cocoa and melted chocolate and stir until well mixed. Finally fold in the pear pieces and pour the mixture over the biscuit base.
Bake for about 60 minutes or until firm to touch. Turn off the oven and leave the cheesecake to finish cooking in the warm oven for 1 hour. Chill thoroughly before serving dusted with a little icing sugar, if liked.