1. To make the ice cream, cut the skin from the mango with a sharp knife, cut the flesh from the stone and chop finely. Whisk the cream, Cointreau, icing sugar, mandarin zest and juice together until it holds its shape. Fold in the mango. Tip the mixture into a rigid container and freeze for 3 hours until softly frozen, stirring once after 1 1/2 hours.
2. Meanwhile, make the meringues. Preheat the.oven to 120C/fan 100C/Gas 1/2. Line two large baking sheets with baking parchment and draw 6 x 6cm circles, spaced well apart, on the sheets (use a Dia6cm jar lid as a template.)
3. Whisk the egg whites with a pinch of salt until stiff. Add half the caster sugar and whisk until glossy. Add the remaining sugar, a tablespoon at a time, while whisking. Fold in the nuts with a large metal spoon.
4. Spoon the meringue on to the parchment and spread to make even rounds. Bake for 1 hour, switching the trays round after 30 minutes. The meringues are ready when they are firm and sound hollow if tapped. Cool on the trays then peel off the paper.
5. Sandwich the meringues together in pairs using the ice cream. Put them into a container in a single layer and freeze along with the leftover ice cream. When ready to serve, remove from the freezer and scatter with the extra chopped nuts.