In a medium saucepan, combine the strong brewed coffee and granulated sugar. Stir gently to mix the sugar into the coffee.

Place the saucepan over medium heat. Bring the mixture to a gentle simmer, stirring occasionally. This step is crucial as it helps dissolve the sugar completely.

Once the mixture reaches a simmer, reduce the heat to low and let it cook uncovered for about 20-25 minutes. This will allow the syrup to reduce and thicken. Stir occasionally to prevent sticking.

After 25 minutes, check the consistency. The syrup should coat the back of a spoon. If it’s not thick enough, continue simmering for an additional 5-10 minutes.

Once the desired thickness is reached, remove the saucepan from heat. Stir in the vanilla extract and salt. This adds depth to the flavor.

Allow the syrup to cool slightly before straining it through a fine mesh strainer into a glass jar or bottle. This will remove any coffee grounds and ensure a smooth syrup.

Let the syrup cool to room temperature before sealing the jar. Store in the refrigerator for up to 2 weeks.