In a small frying pan or pot on the stove, add the syrup ingredients and heat on medium-high, whisking to combine. Once it starts simmering, lower the heat to medium-low and simmer about 3-5 minutes, stirring frequently, until sugar has completely dissolved and syrup has thickened just slightly. Remove from the heat and set aside.
Brew two shots of espresso or about ½ cup of very strong coffee. Add to the mason jar with 3 tbsp of syrup and a few ice cubes and shake vigorously for about 1-2 minutes.
Add some more ice to each glass. Divide the espresso mixture between the glasses. Add oat milk to top it up. Stir and enjoy!
