Simmer brown sugar, water, cinnamon, and salt 4 minutes; cool and discard sticks.

Refrigerate syrup in a covered jar.

For each drink, seal 3 espresso shots, 2 tablespoons syrup, and 1 cup ice in a shaker.

Shake vigorously 15 seconds until cold and foamy.

Pour into a tall glass; top with 1/2 cup oatmilk without fully stirring.