In a medium saucepan, combine the water, sugar, chopped pears, vanilla, and cinnamon sticks. Stir well to combine. Heat over medium-high heat until the sugar has dissolved. Once dissolved completely, reduce heat to low and allow the simple syrup to simmer for 25-30 minutes. The mixture should thicken slightly and be fragrant.
Remove from the heat and allow to cool. Strain the syrup through a fine mesh sieve, discard pear chunks and cinnamon sticks. Transfer to an airtight container.
For the Gin Fizz:
In a cocktail shaker combine gin, simple syrup, lemon juice, and egg white. Place lid on and shake well for 30-60 seconds. Add in the ice and shake again for another minute or two until the shaker is very cold. Strain into a glass, top with sparkling water and any remaining foam from cocktail shaker. Garnish with a pear slice and ground cinnamon.
Cinnamon pear simple syrup will keep in an airtight container in the fridge for 2-3 weeks.
Notes
*If you do not have cinnamon sticks you should substitute 2 tsp ground cinnamon - note it will change the color slightly.