Combine the cinnamon stick, water, and sugar in a small saucepan.
Heat gently until the sugar dissolves completely, stirring occasionally.
Let the mixture simmer for 5 minutes to infuse the cinnamon flavor.
Remove from heat, let it cool, and strain into a bottle or jar. Store in the fridge.
2. Prepare the Cocktail:
Add the gin, Cointreau, lemon juice, cinnamon syrup, and egg white to a shaker without ice (this is called a dry shake). Shake vigorously to create a frothy texture.
Add ice to the shaker and shake again until well-chilled.
3. Serve:
Strain the drink into a chilled cocktail glass.
Garnish with a twist of lemon peel for an elegant touch.