Combine the water and sugar in small saucepan and bring to a low boil. Stir to dissolve the sugar completely. Remove from heat and let the simple syrup cool completely.

In a blender or food processor, blend the fresh mango until smooth. If using frozen chopped mango fruit, let thaw completely then puree until smooth.

Obtain the prickly pear puree: carefully peel and chop the fruit of the prickly pear. Place in a fine mesh sieve or chinois and press to extract the juice and pulp. Measure out 4 oz.

In a freezer-safe container, stir the pureed mango, strained prickly pear fruit, and simple syrup. Add in the dark rum and stir well.

Place in a freezer and let the mixture freeze solid.

Remove the frozen mixture from the freezer and chop up into pieces that will fit inside the bowl of a food processor. Process the frozen cubes until the sorbet is smooth and all the ice pieces have been crushed.

Serve immediately, or place back in the freezer for about an hour for a more firm sorbet.