For the raspberry coulis, measure 250g/9oz of the raspberries into a food processor, add the icing sugar and pulse until smooth.
Tip the raspberry purée into a sieve set over a bowl. Use a metal spoon to push the fruit pulp through the sieve. Discard the seeds.
Divide half the diced mango between six sundae glasses. Divide half the blueberries between the glasses, placing on top of the mango. Sit one scoop of ice cream on top of each blueberry layer, drizzle over half the raspberry coulis and half the whole raspberries. Repeat the layering again to use the remaining ingredients and top with the chopped pistachios.