Preheat oven to 200ºC (180ºC for fan assisted ovens), Gas Mark 6.
Unroll the pastry sheet, cut it into 6 equal pieces and line the tartlet tins. Using a fork, gently prick base of the pastry and add a sheet of greaseproof paper on top. Fill with the baking beans and blind bake in the oven for 20 minutes. Remove the beans and paper, brush with beaten egg and return to the oven and cook for another 5 minutes. Allow to cool totally.
Meanwhile gently melt the chocolate for 2-3 minutes, then stir into the mascarpone cheese.
Divide between the cooled tartlets and spread into bases, top with raspberries and dust with icing sugar before serving.