Make the syrup: Combine 1 cup water and 3/4 cup brown sugar in a small pot with 1 cinnamon stick. Bring to a boil, then simmer for 2-3 minutes until sugar dissolves.

Infuse and cool: Remove from heat. Stir in 2 teaspoons vanilla extract. If using, add 3 chai tea bags, cover, and steep for 10 minutes. Strain and let cool.

Prepare the espresso: Brew 3 shots of espresso. In a shaker glass with ice, combine the warm espresso, 2-4 tablespoons of brown sugar syrup, and 2-3 dashes of cinnamon.

Shake it up: Secure the lid and shake vigorously for 1 minute until well-chilled to create a frothy texture.

Assemble the latte: Strain the shaken espresso mixture into a tall glass filled with fresh ice.

Finish and enjoy: Pour 1 cup of oat milk over the espresso mixture. Stir gently and serve.