Combine the brown sugar and water in a saucepan. Bring to a boil and reduce to a simmer. Let simmer for 1 minute, making sure that all of the sugar has dissolved.
Add the pumpkin purée, sweetened condensed coconut milk, and pumpkin pie spice.
Whisk until smooth. Cook for 3 minutes.
Remove from the heat and stir in the vanilla extract.
It will thicken as it cools. Pour into an airtight container and store in the fridge.