Let the milk bubble up. Stir the salep powder well with 1/2 cup of the milk. Whisk into the boiling milk. Reduce the heat and simmer everything together for about ten minutes, stirring continuously, until the drink has a slightly thick consistency. Add the sugar, mastic and orange blossom water and simmer gently for a short while. Pour hot into cups and sprinkle with chopped pistachios.
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