1. Brew a shot of espresso using your espresso machine. 2. Fill a glass with ice cubes to chill it. 3. Pour the tonic water into the glass over the ice cubes. 4. Slowly pour the freshly brewed espresso into the glass, allowing the espresso to float on top of the tonic water, creating a layered effect. 5. Optionally, garnish with a slice of lemon or orange for extra freshness and aroma. 6. Stir gently before drinking and enjoy the refreshing combination of espresso and tonic.