Fill a Collins glass with ice.
Pour 45ml sambuca over the ice.
Top with 90ml sarsaparilla.
Stir gently once to combine.
Serve immediately with a straw.
The natural carbonation of sarsaparilla softens sambuca's syrupy density, so a single gentle stir is all you need - over-stirring will flatten the drink and muddy the layered aroma.
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