Technique
Press the mint gently with sugar and water just until aromatic, then add bourbon and fill the cup with crushed ice. Churn from the bottom until the outside frosts, top with more crushed ice, and add the garnish last.
A mint julep is a mixed alcoholic drink, or cocktail, consisting primarily of bourbon, fresh mint, water, and sugar.

TonicDB editorial guide
The Mint Julep is a cold bourbon drink perfumed with mint, not a mint purée. Sugar softens the whiskey, crushed ice supplies controlled dilution, and a large aromatic bouquet makes the simple mixture feel especially refreshing.
Press the mint gently with sugar and water just until aromatic, then add bourbon and fill the cup with crushed ice. Churn from the bottom until the outside frosts, top with more crushed ice, and add the garnish last.
A metal julep cup makes the frost visible and keeps the drink tactile, but a sturdy rocks glass also works. Place the mint bouquet close to the rim so the drinker smells it with each sip without needing shredded leaves in the liquid.
Grinding mint releases bitter plant flavors and leaves fragments throughout the drink. Too little crushed ice is another common error: the packed mound is part of the temperature and dilution control, not merely decoration.
Replace the powdered sugar and water with a small amount of demerara syrup for easier mixing and a deeper caramel note. Start with a quarter ounce, churn, and taste before adding more so the bourbon remains central.
These notes explain how to execute and adapt the recipe shown above. Ingredients and serving traditions vary, so taste and adjust thoughtfully.
Contributed by @alfg