Add oats and a cup of water to a bowl and let soak for 30 minutes. While the oats are soaking, combine the blackberries, panela, 1 liter of water, and spices to a pot. Bring to a boil, then reduce the heat and simmer for 15 minutes.
Remove the star anise and strain out the blackberries, reserving the liquid. Add the berries, and 1/2 liter of water to a blender and blend well. Then strain to remove the blackberry seeds. Return the liquid to the blender with the soaked oats and blend until smooth.
Pour the liquid back into the pot with the panela and fruit infused liquid and stir to combine. Heat gently on low, stirring occasionally, for about 5 minutes.
Remove from the heat and serve warm, or let cool then pour into a glass bottle and store in the refrigerator to serve chilled.