Begin by cutting the vanilla and placing it together with the tonka beans inside a container. Pour hot water over the top and add the sugar. Stir the mixture until the sugar is fully dissolved.
Allow the syrup to sit for one day, giving the flavors time to meld together.
After a day has passed, remove the vanilla and tonka beans from the syrup, which should now be chilled. Mix the syrup with blueberry puree, and transfer the mixture into a clean, airtight container.
By following these steps, you should end up with a delicious syrup that can be used to add a sweet, fruity flavor to a variety of drinks and desserts. Enjoy!