Bring 1 cup water, the brown sugar, and cinnamon stick to a boil in a small pot. Simmer 2-3 minutes, until the sugar dissolves. Remove from the heat and add the vanilla. If using, add the tea bags, cover, and steep 10 minutes. Keep in the fridge for up to 2 weeks.In a shaker glass filled with ice, combine the espresso, 2-4 tablespoons syrup, and a couple dashes of cinnamon. Shake vigorously for 1 minute. Strain into a tall glass with ice. Pour over the milk. Stir to combine. Enjoy!