Mango Castaway

Complements of Epicurious, a wonderful source for great recipes (and other stuff), comes this delicious tropical frozen cocktail.  When sipping of this if you're not dreaming about a beach in the Caribbean then you clearly need another one.  Maybe two.  This makes four servings.

Blend mango, aged rum, coconut rum, milk, and 4 cups ice in a blender until smooth.  Divide among glasses and garnish with a tiki drink decoration, if using.