In a small saucepan combine sugar, mango nectar, and ginger. Cook and stir until sugar dissolves. Transfer mixture to a bowl and cool to room temperature.
Strain mixture through a fine-mesh sieve, pressing on ginger to extract any liquid; discard ginger. Place half of the sugar-mango mixture and half of the mangoes into a blender container. Cover and blend until smooth; transfer mixture to a bowl. Repeat with remaining mango-sugar mixture and mangoes. Transfer to the bowl and stir in cream. Cover and chill for at least 4 hours or up to 24 hours.
In a 4- to 5-quart ice cream freezer, freeze chilled mixture according to manufacturer's directions. If desired, transfer to a freezer container. Cover and ripen in the freezer for at least 4 hours.