Preheat the oven to 110C/225F/Gas ¼. Line a baking tray with greaseproof paper.
Whisk the egg whites and lemon juice in a bowl until they form stiff peaks, then fold in the sugar and pistachios. Spoon the mixture into a piping bag fitted with a plain nozzle and pipe small nests onto the baking tray. Bake in the oven for two hours, lthen remove from the oven and set aside to cool completely. Carefully remove the meringues from the paper.
Spoon the melted chocolate into the meringue nests. Whip the cream in a bowl until stiff peaks form when the whisk is removed. Spoon the cream into a piping bag fitted with a small nozzle and pipe into the middle of the nests.
Shave the white chocolate over the nests and decorate each one with a raspberry and a mint leaf.