Pour the Cognac, simple syrup, and lemon juice into a cocktail shaker and add the ice. Shake for at least 30 seconds (it's longer than you think!). Pour the mixture into 4 Champagne flutes to fill each glass about two-thirds full. Fill the glasses with Champagne, garnish with the lemon zest, and serve ice cold.
Ina halved this recipe for taping.
"Cooking for Jeffrey" by Ina Garten © Clarkson Potter 2016. Provided courtesy of Ina Garten. All rights reserved.