In a small saucepan, whisk together brown sugar, water, ground ginger and apple pie spice. Heat mixture over low-medium heat, stirring frequently with a wooden spoon to prevent burning.
Heat mixture until boiling, then continue to simmer on low, uncovered, until the mixture is reduced by half, and becomes thick and syrup-y. Continue to stir frequently.
Let stand for 5 minutes to cool a bit, then stir in the vanilla extract. Transfer to an airtight container to store; keeps in the refrigerator for at least 1 week.