Add the chilled champagne, ice cubes, and simple syrup into the blender.
Blend on high speed until the mixture is smooth and has a slushy, granular texture, about 30-40 seconds.
Pause to check the consistency; it should be icy yet scoopable, with tiny ice crystals visible throughout.
Pour the slushie into chilled glasses, dividing evenly between them.
Garnish each glass with a twist of lemon zest for a burst of citrus aroma and visual appeal.
Serve immediately while still icy, allowing the bubbles and aroma to be fully enjoyed.
