In a small saucepan, combine 2 cups water + 3/4 cup sugar + 1-1/2 cups fresh mint leaves (basil is also fantastic). Bring to a boil and simmer for a few minutes. Remove the leaves, and let cool. Then add to 1 cup fresh lemon juice (about 8 large lemons worth) + 1-1/2 cups water. Serve over ice, and garnish with fresh mint leaves & lemon zest.
For a great cocktail, start with about 2/3 of a glass of the lemonade, add gin, and top off with Citron Perrier.