You will need :
Rum (White of Brown)
Fresh Mint leaves
Sprite or any lemon-lime flavored soda
Here we go :
In a glass bottle, poor as much rum as you might need. stuff the Mint into the Rum - lots of fresh mint.
Cover the glass bottle with a plastic lid - NO METAL - if you don't have a lid, a small plastic or porcelain plate will do.
Get your bottle in the microwave oven, and nuke on high until the rum starts boiling.
Once it does, stop the Microwave.
Let the Rum and Mint stand for 3 to 5 minutes. The Rum will take all the aroma of the Mint.
It is important to keep the lid on top of the bottle until the mix cools down to room temperature, otherwise the alcohol will evaporate. Which would be a shame.
In a glass, squeeze some fresh lime juice. Cover with crushed ice.
Add the Minted Rum.
Pour the Sprite.
Decorate with some fresh Mint leaves.
Adjust the amount of Lime, Rum and Sprite to your taste. If you really don't like the sweetness of the Sprite, you can use some seltzer instead.
Note : you can prepare lots of minted rum this way and store it, you won't even need to mix it the next time...