Step 1: Combine brown sugar and water in a medium saucepan. Make sure to use a saucepan with a bit of extra room as the mixture will bubble up slightly.
Step 2: Place the saucepan over medium heat. Stir gently and continuously until the brown sugar has completely dissolved in the water. Avoid stirring too vigorously, just enough to help the sugar melt. This is crucial for a smooth brown sugar syrup recipe.
Step 3: Once the sugar is fully dissolved and the mixture begins to simmer, reduce the heat to low. Let it gently simmer for 3-5 minutes. Do not boil vigorously; we want the sugar to fully integrate without excessive evaporation. This simmering period helps the flavors meld and thickens your brown sugar syrup recipe slightly.
Step 4: Remove the saucepan from the heat. If using, stir in the vanilla extract now. The residual heat will help infuse the vanilla flavor without cooking it off. Allow the brown sugar syrup recipe to cool completely at room temperature. As it cools, it will thicken further to the perfect consistency.
Step 5: Once cooled, transfer the homemade brown sugar syrup recipe to an airtight container or a clean glass bottle. Store it in the refrigerator, where it will keep fresh for up to 2-3 weeks. Give it a gentle shake before each use, as some settling may occur.