In a small bowl or jar, combine brown sugar with warm water, adding vanilla extract, ground cinnamon, and a pinch of salt. Stir until mostly dissolved.

Fill a tall glass with ice cubes to the brim.

Pour cold brew coffee over the ice-filled glass.

Add the brown sugar cinnamon syrup into the coffee-filled glass and stir well.

Slowly pour in oat milk to the glass and watch it swirl with the coffee mixture.

In a small cup, whisk heavy cream until lightly frothy.

Gently spoon or pour the frothed cream over the coffee and oat milk mixture.

Dust a pinch of ground cinnamon over the creamy topping if desired.