Put a slice of lime on the bottom of the glass. Add pastis.Add aprx 4-3 cubes of ice. Add gin. fill with the bitter lemon, pref. Schweppes. Somehow the drink tastes better if you use bitter lemon from a small Schweppes bottle which has been open for a about 20 secs. Pour the Bitter lemon from as high a s possible, a bit like the proper way to pour tea. don't use ice cubes which are too big, that way the liquids don't mix too well en you have to wait too long and the ice will be melted partly before you serve.
Serve in a Highball Glass