Place the mango, icing sugar, orange liqueur or juice, ginger, and nutmeg in a bowl and gently toss to combine. Cover and marinate at room temperature for 30 minutes, before gently tossing again. Place a row of the mango mixture down the centre of each crêpe; reserving a few slices of the mango to garnish the top. Roll up the crêpes and place one on each of six dessert plates. Garnish each crêpe with a dollop of whipped cream, a few slices of the reserved mango, and a mint sprig.