At medium-low temperature, heat the saucepan for a few minutes.
Put the brown sugar and water in equal amounts in the saucepan. Alongside them, add the maple syrup, salt, and cinnamon stick.
As the mixture heats, continue stirring until the sugar dissolves and the mixture turns amber-brown. This should take about 2 minutes.
Turn off the heat and let the mixture cool for several minutes until it stops steaming. As it cools, the syrup turns sticky because the sugar and water molecules combine.
When the syrup reaches room temperature, transfer it to the sterilized bottle, and ensure it is airtight to prevent it from hardening due to air exposure. You can leave the cinnamon stick in the syrup for up to 24 hours at room temperature and remove it after.
Use the syrup immediately or keep it in your fridge for up to 1 month.