Add all ingredients to a cocktail shaker and shake over ice until well-chilled.
Strain into a chilled coupe glass.
Garnish with a mango slice shaped into a snowflake (with a cookie cutter or knife).
Combine sugar, water, and cinnamon sticks in a small saucepan over medium heat. Bring to a simmer, stirring occasionally, until sugar is dissolved. Remove from heat and let sit at room temperature overnight.
Remove cinnamon sticks and store syrup in an airtight container in the fridge for up to three weeks.