First, you will need a bottle of quality bourbon. I leave the choice of brand to you, but bourbon is one of those things where you really do have to pay more for quality, and bad bourbon will not do (except maybe as the name of your next garage band),
Next, you will need a mint plant. It is essential to use fresh mint. Better quality grocery stores stock them, as do home improvement stores like Home Depot and Lowes. Go get one. I'll wait.
Good. Put two cups of water in a saucepan over low to medium heat. Now pick a half-dozen nicely formed leaves, crush them and add them to the water. Add two tablespoons of sugar. Stir constantly until the sugar is dissolved and the mixture begins to fill the room with a minty smell. You're almost there.
Now, pour some bourbon in a highball glass. Put some crushed ice in a glass bowl. Pour that sugar water crap down the sink, call your bookie to get some bets down on the ponies and enjoy your bourbon.