Making the sorbet: Add the frozen mango, mint leaves, and about a cup of filtered water to the high speed blender. Using the tamper, push and blend until you have a thick consistency. You will need extra water to get the frozen fruit moving along in the blender, I suggest trickling in about ¼ cup at a time until well blended. Taste the sorbet and add honey if needed. Blend once more to incorporate. Pour and evenly spread the sorbet into a 9x5 bread pan and place in the freezer for a minimum of 2 to 3 hours. If leaving overnight, cover with saran wrap and foil.
Making the cocktail: Remove the sorbet from the freezer. If left overnight, let it thaw for at least 10 minutes so it will be easier to scoop. In two rocks glasses, add the juice of 1 lime to each. Slap the mint to bring out the oils to the surface and add 4 leaves to each glass. Add 1.5 to 2 oz of rum to each drink (leave out for mocktails). Add 2 scoops of the sorbet to each and then pour the seltzer over each glass. Garnish with more mint.
How to drink: Add a straw and mix the drink a little to blend the sorbet into the seltzer. Enjoy with a straw and a spoon.