Bring the 4 cups of water to a boil on the stove, reduce heat. Add the mint leaves and let them simmer for 5 minutes.
Remove from heat and stir in sugar.
Let cool to room temperature. Add lemon juice and 5 cups of waters. Refrigerate overnight.
The next morning, strain the mixture through a cheese cloth to remove the mint leaves.
Serve with ice, a pretty straw and a garnish of lemon or mint if desired.
This recipe is based on my tastebud's preferences. Feel free to adjust the mint, lemon juice, water or sugar to suit your tastes.