In a small saucepan, combine 1 cup dark brown sugar and ½ cup water. Stir until the sugar dissolves.
Add ⅓ cup unsulphured molasses, 1 tsp cinnamon, ¼ tsp ground ginger, and ¼ tsp nutmeg to the saucepan. Stir until the mixture is smooth.
Bring the mixture to a simmer over medium heat, stirring occasionally. Let it simmer for about 5 minutes until the syrup thickens slightly.
Remove from heat and stir in 1 tsp vanilla extract.
Allow the syrup to cool before using.
Store in an airtight container in the refrigerator for up to 2 weeks.