Pull 3 ristretto shots of espresso into an 8-ounce cup.
Stir in 1 ounce brown sugar syrup.
Steam about 5 ounces of oat milk, either using the steam wand on your espresso machine, with a handheld or electric milk frother, or in a jar in the microwave.
Pour the steamed oat milk over the espresso and syrup mixture.
Sprinkle cinnamon over the top.