There’s not even really a “recipe.” Here’s what you do:
Buy a carton of high-quality lemonade – I like Newman’s Own All Natural Virgin Lemonade. Shove a large sprig or two of mint through the opening, then seal it up and let it sit in the fridge for at least 24 hours to really let that mint flavor mingle with the lemonade.
Pour some white rum (to taste – I use one shot glass full for about 6 oz of lemonade) into a largeish drink glass with ice. Add the the minty-lemonade, about 2/3 full. Top with club soda and give a quick stir.
You are done! Sit back, take a sip, and think about all the time you just saved.