Step 1
Place two-thirds of the mango in a blender. Add the icing sugar and lime juice and blend until smooth. Transfer mango-lime mixture to a large bowl.
Step 2
Place the remaining mango in a clean blender. Add the rum and blend until smooth.
Step 3
Place boiling water in a heatproof bowl. Sprinkle over the gelatine. Stir until the gelatine dissolves. Add to the mango-lime mixture and stir to combine. Use an electric mixer to whisk the cream in a large bowl until firm peaks form. Add three-quarters of the cream to the mango-lime mixture and use a metal spoon to gently fold until just combined. Whisk the egg white in a clean, dry bowl until soft peaks form. Add to the mango-lime mixture and gently fold to combine.
Step 4
Spoon one-third of the mango-rum puree among serving glasses. Carefully top with half the mango-lime mixture. Continue layering with the remaining mango-rum puree and mango-lime mixture, finishing with the mango-rum puree. Place in the fridge for 2 hours to chill.
Step 5
Meanwhile, to make the coconut praline, line a baking tray with baking paper. Place the sugar in a medium frying pan over medium heat. Cook, stirring occasionally, for 5 mins or until sugar melts and caramelises. Carefully pour over the lined tray. Sprinkle with pistachio and coconut. Set aside for 10 mins to set. Break into shards.
Step 6
Finely chop 1 shard of coconut praline. Top mousse cups with remaining cream. Sprinkle with chopped coconut praline. Serve with remaining praline.