Combine the brown sugar, water, and cinnamon in a small saucepan over medium heat. Stir occasionally until the sugar completely dissolves, and add the vanilla extract. Remove from heat and allow to cool. Once cool, pour into a glass storage container or Mason jar for storage in your fridge for up to a couple of weeks.
Add the oat milk and 1-2 teaspoons brown sugar cinnamon syrup to an automatic milk frother. Warm and froth the milk to your liking. Alternatively, you can add the milk and syrup to a saucepan and gently warm over low heat until it reaches your desired temperature. Use a hand frother or mixer to give it a bit of foam. Pour into your favorite mug.
Pull a shot or two of espresso or make "copycat" espresso as indicated above and combine it with the frothed milk.
For an extra treat, add the plant-based heavy cream and sugar to the frother or use a hand mixer to whip the mixture until it forms stiff peaks. Spoon over your latte, give it a sprinkle of cinnamon, and enjoy!